Bechoros 29a - Payment for Mitzvos

The Mishna says that one is not allowed to receive payment for judging, testifying, or doing the mitzvos associated with para aduma, and if one receives payment he is penalized that we invalidate what he did. The gemara explains that this is based on a general principal of מה אני בחנם אף אתם בחנם, which is learned from a pasuk that demands that we model ourselves after G-d and not take payment for the doing of mitzvos such as teaching Torah or paskening on questions. Although there is already a prohibition against a judge taking a bribe, Tosafos explains that this source is necessary to forbid him from taking payment that is not meant to influence the outcome of the judgement (but if it influences the outcome in either direction, it is regarded as a bribe).

When the gemara cites the source for not accepting payment as being the requirement to model G-d and do it for free, Rashi gives the examples of authorizing a p'sak i.e. din, and teaching Torah. Rashi fails to mention the issue of testifying and preparing the para aduma waters. The Cheishek Shlomo suggests that accepting payment to testify according to Rashi is only prohibited m'drabonon, not from the Torah. If it were forbidden m'doraysa it would be tantamount to a witness taking money to testify falsely categorizing him as a רשע דחמס and being passul for all testimonly. The Mishna implies that we only invalidate this testimony, implying that his violation isn't d'oraysa. It also isn't clear from Rashi whether payment for other mitzvos is forbidden m'doraysa or only m'drabonon.

The Rashash cites the Bartneura who elaborates about those who officiate gittin and take payment. He is assuming that sidur ha'get qualifies as din and would invalidate the gett. However, the Rama (E.H. 154) says that it doesn't qualify as din, just as limud ha'torah. The Rashash points out that this would justify the gett being kasher, but wouldn't justify the practice to accept payment for officiating a gett since it would still be a violation of מה אני בחנם אף אתם בחנם as we find by talmud torah. Tosafos justifies those who take payment for studying Torah based on the דייני גזירות in Yerushalayim who relied on this for their livelihood and therefore became the community responsibility to support them so that they can maintain their important work. This logic may also apply to mesadrei gittin or those who do other mitzvos i.e. milah for their livelihood. Someone asked me how I can charge to do a bris - i answered that the mitzvah of bris milah is to cut. I don't charge for the mitzvah of doing a bris, I only  charge for stopping the bleeding.

Bechoros 25a - More about Davar She'eino Miskavein

The gemara suggest that R. Yossi Ben Meshulam agrees with Rav (who paskens like R. Yehuda) that דבר שאינו מתכוין is forbidden. How then does he permit the cutting of the black parts of the hairs of the פרה אדומה leaving behind only the red parts, although he isn't intending to be גוזז but to fix the parah a'duma, it should still be a violation? The gemara implies, and Rashi explains explicitly that since his intent when he is cutting the black parts of the hair is to fix the cow rather than take the hairs, it would be considered a דבר שאינו מתכוין. Tosafos points out that this seems to be a very strange application of דבר שאינו מתכוין. Normally a דבר שאינו מתכוין is where one doesn't even intend to do the ma'aseh issur, but where one intends to do the act of issur just that he is doing it for a different purpose than it is normally done for, it would be considered a מלאכה שאינה צריכה לגופה (which is a special p'tur in hilchos shabbos due to מלאכת מחשבת- it doesn't apply to other areas of halacha and even on shabbos is exempt from punishment but forbidden). In this case where the person is cutting the hairs of the parah a'duma intending to do the act of cutting, it would be similar to a standard מלאכה שא"צ לגופה, but shouldn't qualify as a דבר שאינו מתכוין? Tosafos asks this question in very few words -

 דאין זה כשאר לשון "אין מתכוין" בעלמא דכיון דבכוונה גוזז במספרים. Why does the gemara consider this to be a davar sh'eino miskavein? 

It seems to me that by certain מלאכות the purpose of the act is so integral to the melacha, that when the act is done for a different purpose it is tantamount to not intending to do the act at all. The prohibition of גוזז on kodshim is that it is forbidden to do things that enable one to take the products of the animal (whether it is the wool, the work in the field or the milk), while it is still alive. Although Tosafos (d.h. sa'ar) explains that the issur is a ma'aseh issur of cutting the wool, unlike the issur of the milk which is an issur on the product, the nature of the issur to cut the wool is because normally one would do this act to obtain the product. When one is גוזז but has no interest in the wool, it undermines the act of גוזז to the point where we consider him to not be intending for גוזז at all. Therefore, when he cuts the blackened parts of the hairs for the purpose of fixing the parah aduma, not for the purpose of using the hairs, it is considered as if he isn't intending to do the act of issur.

Bechoros 24b - Davar Sh'eino Miskavein

There is a machlokes between the Teruma HaDeshen and the Magen Avrohom whether we can be matir one to do a פסיק רישא דלא ניחא ליה - an inevitable action where he isn't interested in the issur outcome, when the issur is only d'rabonon. The Terumas HaDeshen permits a פסיק רישא דלא ניחא ליה באיסור דרבנן and the Magen Avrohom forbids it (O.C. 314:5). R. Akiva Eiger proves that the Magen Avrohom is correct from a gemara in Succah.

Normally we pasken like R. Shimon that a דבר שאינו מתכוין is permitted, not like R. Yehuda who forbids it. However, when it is inevitable - פסיק רישא, even R. Shimon admits that it is forbidden as the gemara says 25a. When the gemara speaks about a p'sik reisha it is usually in a context where the person is interested in the issur outcome. But when the person isn't interested in the outcome - פסיק רישא דלא ניחא ליה, Tosafos in Kesubos 6a cites the Aruch who permits it even by an issur d'oraysa. Tosafos disagrees and holds that it is forbidden at least by an issur d'oraysa. The Terumas HaDeshen and Magen Avrohom argue if we can be matir by an issusr d'rabonon.

Tosafos explains in our sugya that even though Rav paskens like R. Yehuda who forbids a דבר שאינו מתכוין, that is when the issur is d'oraysa. But if the issur is d'rabonon (either because it is mekalkel, or because תולש לאו היינו גוזז), it would be permitted. It seems that a דבר שאינו מתכוין  according to R. Yehuda is worse than a  פסיק רישא דלא ניחא ליה according to R. Shimon. The Aruch holds that פסיק רישא דלא ניחא ליה is permitted, so even though we hold like Tosafos that it is forbidden, we see that there is grounds to be matir. It would be logical to assume that if Tosafos holds that even R. Yehuda would permit a דבר שאינו מתכוין when it is only d'rabonon, according to R. Shimon who is always matir דבר שאינו מתכוין, but is machmir for a פסיק רישא דלא ניחא ליה, he would at least be meikel when the entire issur is only d'rabonon. This would seem to support the opinion of the Terumas HaDeshen, against the Magen Avrohom. However, the M.B. writes that l'ma'aseh, most achronim agree with the Magen Avrohom to forbid a פסיק רישא דלא ניחא ליה even when the nature of the issur is only d'rabonon.

Bechoros 23a - Understanding Bitul B'rov

The gemara raises a concept of an item which is batul whether it is viewed as כמאן דאיתיה דמי. The gemara assumes that if we regard an item that is batul as if it doesn't exist then when a tamei item is batul it wouldn't even be me'tamei by carrying, but if we regard it as existing even while it is ba'tul it would be me'tamei through carrying but not through touching. The gemara leans toward the distinction between carrying and touching implying that we view the tu'mah to be in existence even while it is batul. The rationale for the distinction between carrying and touching is that when one touches something they cannot be touching every molecule at once. Therefore, we can only consider him to be touching an item of tu'mah if the majority is ta'mei, otherwise we would consider the entity to be not tamei. However, when it comes to ma'sah, since when something is carried, every molecule in it is carried, the existence of the tu'mah even as a minority would render the carrier tamei.

Tosafos (d.h. 23a) asks that eating an item should be more similar to tu'mas ma'sah than to tu'mas ma'ga. Why do we permit one to eat an issur that has been batul in rov? Since the minority is considered to still be in existence, it should be comparable to ma'sah where the entire item is being carried or eaten and therefore should be eating issur? Tosafos answers that when one eats something, every small amount that is swallowed is batul b'rov and is therefore similar to ma'ga where the touching of multiple times doesn't make it as if were touched at once. Therefore, just as by tu'mas ma'ga we would identify the entity based on the majority ingredient, the same would be for eating. Tosafos assumes that it would be impossible to eat the entire amount all at once. Perhaps it is because the בית הבליעה can only contain a beitza at one time which it 2 kezaysim. For there to be a full kezayis of issur in the בית הבליעה at once of something that has been batul b'rov, there would have to be more than 2 kezaysim in the beis ha'blia at one time, which is impossible. Furthermore, there should be an issur of eating even a chatzi shiur of issur, unlike tu'mah for which there is no contamination if it is less than the amount needed to be metamei.

The Rosh (Gid HaNashe end of 37) asks the very same question as Tosafos except that the Rosh preempts the answer of Tosafos in his question and says that one should have to be careful to eat in a way where every swallow could potentially contain only the heter food and not the issur food so that it would be more similar to ma'ga than ma'sah? The Rosh answers that we cannot compare tu'mah to issur. There are two types of tu'mah, therefore the chiddush of bitul b'rov may apply to one and not the other, such as to ma'gah and not ma'sah. However, regarding eating, if we would consider there to be any issur in what the person was consuming, the Torah wouldn't allow it's consumption. The fact that the Torah allows one to eat issur that has been ba'tul is a gezeiras hakasuv that in the world of issur, we view it כמאן דליתיה דמי, as if it weren't in existence. Therefore, a piece of issur that is batul in two pieces of heter can even be cooked together (on a torah level) and eaten all together as if the issur disappeared.

The approach of the Rosh seems to assume that the concept of tu'mah that has been batul being metamei by carrying to be d'oraysa, whereas Tosasfos concludes that it is likely only m'drabonon.

Bechoros 22a - Shiur for Opening of Uterus

The gemara quotes the Mishna in Ohalos (7,4) which says that the shiur for pesichas ha'kever is עד שיעגילו ראש כפיקה. The gemara explains that it is the size of a פיקה של צמר which is used for the שתי stitch. The context of the mishna is to know at which point the cervix is considered open enough so that the dead fetus inside can no longer be considered טומאה בלועה and will be me'tamei the vessels that are in the same room as her. It is unclear if this is also the shiur for פתיחת הקבר in the context of the statement in nidah - אין פתיחת הקבר בלא דם. The Nodeh B'Yehuda cited by the Pischei Teshuva (Y.D. 194,4) says that even forcing the cervix open from the outside would qualify as an opening of the cervix and we would have to be concerned that some blood was let out of the cervix. R. Moshe (Igros Moshe Y.D. 1, 83) says that although the binas adam and chasam sofer disagree with the nodeh b'yehuda, they only disagree when one would use a finger to open the cervix because they assume that a finger wouldn't reach through the cervix. However, even they would agree with the Nodeh B'yehuda that if a tool or instrument is used to enter the cervix, it could qualify as an opening of the cervix where we would say אין פתיחת הקבר בלא דם. R. Moshe (Igros Moshe Y.D. 1, 89) says that although the Nodeh B'yehuda says that only something with a very small diameter such as a pieces of straw wouldn't be considered an opening of the cervix, implying that if it were slightly larger it would be considered an opening of the cervix rendering her a nidah. R. Moshe disagrees because the only shiur that we find in chazal for the opening of the cervix is the shiur of כפיקה של צמר, which they also term as a פתיחת הקבר, therefore it is logical that this would be the shiur also in the context of אין פתיחת הקבר בלא דם. Although it is difficult to know exactly the size of the פיקה של צמר that is used for the שתי stitch, R. Moshe assumes that it must be smaller than the diameter of a small finger. Being that the Rambam paskens that it is possible to have an opening of the cervix without any bleeding, and it is possible that an externally forced opening wouldn't qualify as a פתיחת הקבר, R. Moshe is confident in being lenient with any instrument where the diameter is less than the size of an average persons pinky finger.

Bechoros 21b - What Can You Assume When Buying an Animal from a Jew?

The gemara has three opinions when one purchases an animal from a Jew and wasn't told whether or not it had already given birth to a Bechor. Rav says that the assumption is that the first born will be a bechor because if the it had already given birth the Jew would have mentioned it to praise his the item he is selling. Shmuel says that it is a safeik since the seller may have assumed that the buyer wanted it to shecht so it wasn't relevant whether or not it had already given birth. R. Yochanan says that the buyer can assume that it is not a bechor because there is an obligation on the seller to notify the buyer if the first born would be a bechor otherwise he would be in violation of lifeni iever (tosafos).

There is a machlokes Rashi, Tosafos and Rabbeinu Gershom within the opinion of Rav as to what the advantage would be in telling the buyer that it had already given birth. Rashi says that it would have more value since the animal born from here on wouldn't have to be given to the kohein. Rabbeinu Gershom says the advantage would be that it is an animal capable of providing offspring. Tosafos (quoting rashi) says that the advantage would be that the animal has proven it is capable of surviving child birth and therefore more valuable. The Maharit Algazi asks although when the seller doesn't say anything we don't have to be concerned that it actually gave birth to a viable child, but why are we not concerned that it miscarried (ti'nuf) which would also exempt the next born from being a bechor? He explains that according to the rationale of Rashi and Rabbeinu Gershom, the logic would apply to ti'nuf as well. According to rashi since ti'nuf exempts from having to give the next born to the kohein, the seller would notify about tinuf as well. According to Rabbeinu Gershom, perhaps even ti'nuf would be an advantage in showing that it is capable of conceiving (although wasn't able to produce a viable offspring). But, according to Tosafos where the advantage is that the animal is capable of surviving childbirth, this wouldn't apply to ti'nuf. According to Tosafos the seller would have no reason to tell the buyer about the ti'nuf so we should be concerned that it was me'taneif and the next born may not be a bechor? Perhaps this is why Tosafos offers an alternate approach.

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Tosafos writes that only a Jew would be believed about the advantage of having already survived a childbirth and therefore being more valuable but a goy wouldn't be believed about this. Tosafos proves from here that even if a goy is מסיח לפי תומו, talking without trying to make a halachic statement, he isn't believed since we assume he is lying to make the item seem more valuable. The Maharit Algazi asks that this implies that if the goy was truly מסיח לפי תומו and not trying to make his item seem more valuable he would be believed even for bechor. But, the gemara says in yevamos that a goy is never believed מסיח לפי תומו on an issur d'oraysa, he is only believed when he is מסיח לפי תומו on an issur d'rabonon, but this is an issur d'oraysa? From this the Maharit Algazi concludes that the Rov of most animals having already given birth after reaching the ages listed earlier in the perek, is a valid rov on a d'oraysa level, just m'drabonon not a good rov since it is dependent on an action (gemara 20a). Since m'doraysa we have a rov that the next born is not a bechor, and it is only d'rabonon that we can't rely on the rov, we can believe a goy if he is truly מסיח לפי תומו without any motive to glorify his item.

Bechoros 19b - Following the Majority

The gemara suggests that perhaps the halacha of following rov only applies to רובא דאיתא קמן, a rov that is in front of us such as the majority of the sanhedrin voting on an issue, or 9 kosher stores and one non-kosher. But a רובא דליתיה קמן may not command the same status and we wouldn't follow it. The gemara rejects this from the fact that we follow the majority in assuming that most children will not turn out to be a s'ris or ay'lonis, even though that is dependent on a statistic of רוב קטנים לאו סריסים ורוב קטנות לאו איילונית נינהו, which is a רובא דליתיה קמן. However, why do we consider the rov by ketanim to be a רובא דליתיה קמן - just as we consider the 9 stores to be a רובא דאיתיה קמן, we should consider the rov of ketanim to be רובא דאיתיה קמן since most ketanim that are alive in the world today aren't s'risim or ay'lonis? Rabbeinu Gershom seems to address this question and writes- דלא חזינא רובא דעלמא אי הוי סריסים אי איילונית אי לא ואפ"ה אזלי בתר רובא. Even though we have a statistic telling us something that exists right now, since the numbers aren't obvious and can't be counted in front of us, it would qualify as a רובא דליתיה קמן. Similarly, the fact that most cows aren't treifos is a רובא דליתיה קמן because the statistic will not create a רובא דאיתיה קמן since they cannot be counted in front of us.

On another note, the gemara says that we don't follow a rov that is dependent on an action such as the fact that most animals would be pregnant by a certain age, which is dependent on the action of mating with a male. The rationale for not following this rov, the Ramban (Halachos of Bechoros) writes that a mi'ut which happens by itself is stronger than a rov that is dependent on an action. Rashba in Chulin 9a says that this limitation is only d'rabonon. Meaning, m'doraysa we follow rov even if dependent on an action but the Rabbonon tell us not to. Therefore, the Chazon Ish writes that we can only be machmir to not follow a rov dependent on an action, but we cannot be lenient to do so. The Binas Adam (sha'ar rov v'chazaka) proves that the Rashba is correct that it is only d'rabonon based on Tosafos ד"ה אי בעית אימא who says that R. Meir who is concerned for the mi'ut is only d'rabonon. Since the first answer of Rava that the concern of the mishna that the animal born now is a bechor is only m'drabonon, the answer of Ravina about not relying on rov which is dependent on an action is also only d'rabonon. However, this proof isn't very solid because when there is a chazaka that supports the mi'ut even R. Meir would agree that we are concerned for the mi'ut even m'doraysa and here there is a chazaka that supports the mi'ut (as tosafos explains in d.h. me'chvarta). The issue of whether R. Meir is concerned for a mi'ut only m'drabonon or even m'doraysa (when there is no chazaka), is a dispute between tosafos and mordechai (mentioned in this blog on the first perek of chulin).

Bechoros 9b - Spending Money for Safeik Mitzva

The Mishna says that if one has a safeik whether they have a peter chamor, they must redeem it with a sheep but don't need to give it to the kohein  since the rule for giving is המוציא מחבירו עליו הראיה - the burden of proof is on the collector. The gemara says that this follows the opinion of R. Yehuda who says that a peter chamor is forbidden to derive benefit from, therefore one must redeem it even though it won't be given, but according to R. Shimon who says that it is permitted, there isn't even a mitzvah to redeem it. 

Tosafos raises an interesting question - A peter chamor without redemption requires it's neck to be broken. Since the mitzvah to break it's neck (arifa) is like any mitzvah where we are strict when there is a doubt, even if it weren't assur b'hanah, there should be a requirement to break it's neck. Tosafos answer cryptically and says that just as one doesn't need to give it to the kohein, there is also no requirement to do the arifa out of safeik. It isn't clear what Tosafos means to say - the concept of המוציא מחבירו עליו הראיה exempts the giving to the kohein but doesn't exempt the breaking of it's neck? 

The Maharit Algazi suggests that since we have a concept of המוציא מחבירו עליו הראיה and apply it even to mitzvos that one is obligated to do by the torah such as all safeik of gifts to the kohein, we can similarly apply this concept to any mitzvah where it is questionable if one needs to fulfill it and the fulfilling of it would entail a loss of money. Since the arifa of the peter chamor would be a loss of money, one isn't required to incur the loss for a safeik mitzvah.

This approach is very difficult to accept. It should follow that if one is in doubt whether they are obligated in matzah on pesach or whether they have already fulfilled their mitzvah, they shouldn't be required to incur any expense to fulfill the mitzvah. Had this been true, it should have been mentioned in earlier poskim. Rather, we generally assume that this rule is limited to mitzvos that require giving, but doesn't apply to expenses that need to be incurred to fulfill mitzvos between man and G-d. Therefore, this concept shouldn't apply to the mitzvah of arifa (breaking the donkeys neck).

The Rashash explains that Tosafos doesn't mean to fully equate the mitzvah of breaking the neck with the giving to the kohein, since the concept of המוציא מחבירו עליו הראיה wouldn't apply to the mitzvah of arifa. Rather, Tosafos holds that the arifa is the consequence when one doesn't fulfill the mitzvah to give the sheep to the kohein as redemption of the newborn donkey which is incumbent upon him. When there is no requirement to give a sheep to the kohein, the mitzvah of arifa would also not apply.

Bechoros 6b - Heter to Drink Kosher Milk

The gemara says that the fact that milk of a kosher animal is permitted to drink is a chiddush because one could have argued that it would be included in either the prohibition against blood (דם נעכר ונעשה חלב), or the prohibition against אבר מן החי since it is part of a live animal. The gemara cites three possible pesukim as the source of the fact that milk is kosher (either the pasuk when Dovid brought milk to the troops, or the pasuk that praises the land of Israel for it's milk which indicates that it is permitted to drink, or a pasuk in Yeshaya).

The Shita Mikubetzes asks, why not use the pasuk by Avrohom when he fed the angels butter and milk. Being that Avrohom kept the entire Torah, the fact that he was willing to give milk to the angels indicates that it is permitted to drink? The R"I answers that Avrohom thought that they were bnei noach. Even if milk were forbidden to Jews, it wouldn't be one of the 7 Noachide laws and permissible for them to drink it. The Shita then cites a Yerushalmi (which is not in the Yerushalmi but in the pesikta and quoted by the da'as zekeinim on parshas vayera) that indicates they ate meat and milk (unlike the gemara in baba meztia which implies that didn't actually eat, and also says that it was served one by one i.e. milk before meat) . When it came time to give the Torah and the mal'achim were complaining they wanted to keep it, Hashem said that every child knows that meat and milk can't be eaten together, yet they ate meat and milk when they visited Avrohom. It isn't clear how this midrash connects to the discussion of the Shita Mikubetzes. Perhaps the Shita is trying to prove that Avrohom thought they were bnei noach from the fact that he fed them meat and milk, so there wouldn't be any proof from there about milk being permitted to drink.

The Maharit Algazi asks that according to the rationale that milk would be assur as אבר מן החי, it would surely apply to non-jews as well. The answer of the Shita that Avrohom assumed they were bnei noach doesn't work if the issur on milk would be an offshoot of אבר מן החי? The Chasam Sofer (y.d. 70) answers that the gemara never really suggested that milk would actually be אבר מן החי or בשר מן החי because it is neither an ei'ver or ba'ssar. Rather the gemara was suggesting that it should be LIKE אבר מן החי in the sense that it would be assur (not not for goyim), based on concept of הטמאים - לאסור צירן ורוטבן וקיפה שלהן. Meaning, since אבר מן החי is assur and the animal is assur when it is alive, so anything that comes from it when it is alive should be included in the prohibition of הטמאים. This prohibition would certainly apply to Jews only, therefore Avrohom would have had no problem giving milk to b'nei noach.

Bechoros 5b - Categorizing Animals Based on Features or Genetics

The Mishna discusses a case where a mother cow gives birth to a child that looks like a donkey. The gemara learns from the pasuk of פטר חמור that the child would not have Kedushas Bechor. It is clear from the gemara that we completely exempt it from any kedusha of bechor, but it isn't clear from the gemara which type of kedusha it would have if not for the pasuk excluding it. Meaning, do we regard it as a cow since genetically it is a cow, just that it looks like a donkey, or do we regard it as a donkey since it looks like a donkey?

It would seem that the answer lies in the end of the Mishna which cites a rule that היוצא מן הטמא טמא והיוצא מן הטהור טהור. The mishna seems to indicate that the genetic makeup of an animal determines the species to which it belongs, therefore an animal born from a kosher animal (even if it looks like a donkey) is kosher. Similarly, an animal born from a non-kosher animal (even if it looks like a cow) is not a kosher animal. If genetics determines the category, we would have to say that a cow that gives birth to a donkey would have been treated like a בהמה טהורה and been brought as a korban on the mizbei'ach, if not for the pasuk excluding it.

However, the implication of the mishna which uses a pasuk of פטר חמור to exclude this case, implies that we really need the pasuk to exclude it from the requirement of פטר חמור, not from kedushas mizbei'ach (although the gemara confirms that it would certainly be excluded from kedushas mizbei'ach as well). The Steipler (4) proves from Tosafos that this is true. Tosafos suggests that for a cow that gives birth to a donkey the pasuk of the mishna (פטר חמור) would be necessary to exclude if from the mitzvah of redemption like a donkey, and the pasuk in the gemara would be necessary to exclude the reverse (a donkey giving birth to a cow) from kedushas mizbei'ach. Although Tosafos concludes that either pasuk would exclude it completely, their logical default for not having a pasuk would be that the animal should be treated as it looks, not as the species of it's mother. Meaning, a cow that gives birth to a donkey would have been treated like a donkey to require redemption despite that it's genetic makeup is that of a cow. The Steipler proves from here that the species of any animal is determined by it's appearance, not by it's genetics. Nevertheless, there is a separate rule that if it looks like a kosher animal but is born from a donkey, it cannot be eaten - היוצא מן הטמא טמא, not because it's a donkey, but because it is a non-kosher cow. Similarly, if it looks like a donkey it is a donkey, yet if born from a cow it can be eaten because היוצא מן הטהור טהור. This approach of categorizing a donkey born from a cow as a "kosher donkey" is significant because for purposes other than eating i.e. eiver min ha'chai it would have status of what it looks like, not what it is genetically.

The gemara 6a seems to strongly support the approach of the steipler that the species is determined by it's appearance rather than it's genetics. According to the rule that having similarities to it's mother can make it have kedusha of bechor, the gemara questions whether a donkey that has similarities to it's mother which is a cow, would have kedusha. The gemara's suggestion of why it is too different from the mother and wouldn't have kedusha is - הא טמאה והא טהורה, הא קדושת הגוף והא קדושת דמים. The gemara describes it as a non-kosher animal and as the value having kedusha rather than inherent kedusha. Clearly, the gemara is understanding that since it looks like a donkey, if it were to have kedusha (because it has similarities to the mother), it would have קדושת דמים like any donkey, not קדושת הגוף like it's mother.

Bechoros 3b - Avoiding Kedushas Bechor

The gemara discusses exactly how much of an animal must be given over to a goy in order to avoid kedushas bechor. The predominant opinion seems to be like R. Huna that the ear is enough, since we find that Rami Bar Rachel did that as well. Tosafos entertains the possibility that we would pasken that one would have to give over to the goy a portion in the animal that if missing would render the animal a neveila or treifa (rav chisda and rava), but considers it to be a chumra. Regarding the fact that one is removing kedusha from animal entirely by selling a portion to a goy, Tosafos suggests that it would only be an issue if one were to sell a portion of the fetus which itself would have otherwise had kedusha, but would not be an issue when selling a portion of the mother. Even though this may not be ideal, Tosafos considers it the proper thing to do nowadays since there is no better alternative and if this isn't done someone will surely violate a more severe prohibition with the animal.

The Turei Even (Rosh HaShana 13) suggests that being mafkir the animal would NOT be sufficient to remove the kedusha of bechor from the fact that Rami Bar Rachel who was looking for the simplest option, didn't use the method of hefker. The Chasam Sofer (Y.D. 316) dismisses the proof since it could be that a proper hefker in the presence of others could have been more complicated and difficult than simply selling the ear to a goy. The Maharit Algazi suggests a complicated approach. Hefker wouldn't work to remove the obligation of bechor on an animal that already has kedushas bechor. However, if one were to be mafkir the fetus prior to it's birth, since at the time when it would be fit to receive kedushas bechor it doesn't have an owner, it wouldn't get kedushas bechor. He then backs off based on a gemara in Chulin and says that even if born as hefker, as soon as a Jew would take possession of it, it would assume kedushas bechor.

Chulin 141b - Punishing for Shiluach Hakein

The gemara says that R. Yehuda gave malkus to someone who clipped the wings of a bird and then sent it away on its feet to fulfill the mitzvah of shiluach hakein because he holds that it must be sent away by flying, not by hopping. The Mishneh L'melech (hil. avadim 18) asks how he was able to punish for this mitzvah. We have a rule - כל מצות עשה שמתן שכרה בצדה אין ב"ד של מטה מוזהרין עליו, meaning that Beis Din doesn't punish for any mitzvah that has a reward tagged onto it. How was R. Yehuda able to punish for shiulach hakein which has the reward of long life attached to it? 

The Maharatz Chiyus suggests based on Rashi (?) that the reason that beis din doesn't punish when there is a reward attached is because by writing the reward the torah is hinting that the this is the reward for doing it and not receiving this reward is the punishment for not doing it, to the exclusion of any other punishment. The Maharatz Chiyus explains that this rule works by other mitzvos, but by shiluach hakein the mishna 142a says that the reward needs to be written to teach that there is tremendous reward even for small mitzvos such as this for which there is very little expense. From here we derive that for all mitzvos there is great reward, making it unnecessary to dictate the specific reward if not for the purpose of exempting you from any other punishment. Therefore, shiulach hakein is an exception to the rule since it serves as the source for teaching that there is great reward for even seemingly simple mitzvos, and is not meant to exclude any other punishment.

It seems to me that Rashi himself is coming to answer the question as to how R. Yehuda was able to punish for a mitzvah that the torah writes the מתן שכרה בצדה. Rashi says that the purpose of his "punishment" wasn't punitive, rather it was רידוי בתוכחה שלא ירגיל בזה, ואין לה קצבה אלא עד שיקבל עליו. Meaning, the purpose was not to punish, rather to change the person and motivate him to fulfill the mitzvah. Although Beis Din may not "punish" or "penalize" for mitzvos on which a reward is tagged on, they may still have the ability to encourage and motivate one to fulfill the mitzvah even through force.

Chulin 139b - Searching after mitzvos

The gemara says that one may have thought that they would be required to search after the mitzvah of shi'luach ha'kein and put in effort to find a birds nest on mountains and hilltops, to which the gemara responds that it only applies when you chance upon it. There is a great debate among the achronim regarding the mitzvah of shiluach ha'kein, whether it is an absolute obligation to send away the mother bird even if one has no particular interest in the baby birds, or is it a mitzvah more similar to divorce where if one wants to do something i.e. take the babies, or divorce their wife, the torah prescribes a format that must be followed. The Chacham Tzvi (83) and Chasam Sofer (100) suggest from this gemara that thought to demand searching after the mitzvah on mountain tops, that it is an absolute obligation. Although the gemara concludes that one isn't obligated to go to the extreme of trying to locate a birds nest, the underlying assumption that it is an absolute imperative even if one has no interest in the babies is never rejected.

On a bit of a different note using the same source, the Mekor Chaim (Nesivos on Hil. Pesach Siman 432) which I cited in my sefer Nasiach B'chukecha (195) proves from our gemara that one is required to invest effort into searching after mitzvos from the fact that the gemara required a specific pasuk to exempt the assumption of searching after the mitzvah on hilltops. Therefore, other mitzvos that don't have a pasuk exempting this level of effort, would demand that extreme amount of effort. However, in my edits on my sefer I pointed out that from Rashi we would be able to prove the exact opposite. Rashi writes - 

שנאמר שלח תשלח ב' פעמים, שומע אני לחזור אחר המצוה הזאת עד שתבא לידו. Rashi explains that the default position for having to put tremendous effort into searching after this mitzvah is not a gobal requirement or assumption that would be by all mitzvos. Rashi says that since we have the double language of שלח תשלח I would have understood that this mitzvah would require one to search after it in order to fulfill it, to which the gemara responds that כי יקרא implies the opposite. Therefore, other mitzvos which have no pasuk specifically implying that it demands an extreme level of effort, one would not have to put in tremendous effort to attain the mitzvah.

Chulin 135a - Reishis Ha'Geiz and Matnos Kehuna Nowadays

According to the Mishnayos both the mitzvah of ראשית הגז  and the mitzvah of מתנות כהונה apply without a Beis HaMikdash and even outside of Eretz Yisroel. However, Rav Nachman 136b made a statement that the minhag is to follow רב אלעאי by ראשית הגז and that it should only apply in E.Y. Rashi comments - והוא הדין במתנות, meaning that there is no rationale to differentiate between ראשית הגז  and the matanos of זרוע לחיים וקיבה. Since the minhag has become to follow רב אלעאי by ראשית הגז, we also follow him for matanos kehuna that they don't apply outside of E.Y. The Shulchan Aruch both in the halachos of Matanos Kehuna (y.d. 61:21) writes that they apply even outside of E.Y. and then cites a יש מי שאומר שאינן נוהגות בחוצה לארץ. The Shulchan Aruch in the context of matanos kehuna writes וכן נהגו on the lenient opinion even though the main opinion seems to obligate matanos even outside of E.Y. Interestingly, the Shulchan Aruch in the context of reishis ha'geiz doesn't even quotes the stricter opinion - he writes that it only applies in E.Y. to which the Rama adds that some says it applies even on a Torah level in chutz la'aretz but we aren't noheig to be machmir. The Shulchan Aruch is more confident about exempting from reishis ha'geiz in chutz la'aretz since that is explicit in Rav Nachman's statement. Although there is no rationale to differentiate between reishis ha'geiz and matanos, the gr"a (61:20) explains that the leniency is based on a minhag which may have only been to be lenient about reishis ha'geiz and not about matanos kehuna. The Beis Hillel (333) struggles with trying to understand why we are even lenient in E.Y. nowadays. Although the Pischei Teshuva (61:8) cites the chasam sofer who would routinely shecht an animal before yom tov and fulfill the mitzvah of matanos kehuna and reishis ha'geiz, the minhag is not to be makpid about fulfilling these mitzvos. The Beis Ephraim (on shulchan aruch 61) quotes the kerisi u'pleisi who wonders why we don't find people going out of their way to fulfill this mitzvah. He quotes the Pri Chadash who argues on the Beis Hillel's (who wrote that he was told that even in E.Y. people don't fulfill the mitzvah of matanos kehuna), and says that they didn't realize what they saw because it is מעשים בכל יום that matnos kehuna are given in E.Y. from the animals that are being shechted. The Beis Ephraim also quotes that the kreisi writes that his son in law insisted on giving matanos kehuna at the pidyon ha'ben of his son. Since he was being machzik the kohein as a kohein for the purpose of discharging his pidyon ha'ben obligation, he certainly can rely on his yichus to give him matnos kehuna.

Chulin 122b - How far do you have to go?

The gemara says that for tefilah and netilas yadayim one must travel 4 mil forward, and just under one mil backward. Rashi explains that we are talking about someone who is on the road travelling and he wants to stop for the day, but knows that he will have a shul 4 mil ahead to daven (Tosafos assumes that this means a minyan, not a physical structure), he must continue to go to the shul. Similarly, if one was hungry and wanted to eat bread but didn't have water to wash his hands, he would be required to wait until he travels 4 mil before he eats.

The Biur Halacha (163) assumes that the shiur of 4 mil is really a time requirement. Since it would take 72 minutes for the average person to travel 4 mil, the gemara is demanding that one wait 72 minutes. A possible scenario would be if one is on an airplane and wants to eat bread but can't leave his seat at the moment, since it is very likely that within 72 minutes he will be able to wash, he is obligated to wait. It isn't clear to me why the Biur Halacha assumes that this would be dependent on time. Rashi uses language of "tircha" implying that one must push themselves to continue to travel, implying that the amount of 4 mil was for a circumstance where he was on foot and walking 4 mil is a significant tircha. Perhaps if he were travelling with minimal tircha he would need to wait longer than 72 minutes.

The M.B. also comments that if one isn't certain that by waiting or continuing to travel they will find the shul or water, they aren't required to wait at all. This is certainly the implication of Rashi who writes in definitive terms that there is water and a shul in front of him.
Another point that the Biur Halacha makes in the name of the Chayei Adam is that if one isn't very hungry he should wait even more than 4 mil. However, Rashi gives an example of one who wants to stop while it is still day and the halacha demands that since it is still day time and easy to travel, he must continue. It would seem that a similar case by eating would be when one wants to eat now but can relatively easily delay. Perhaps if one is very hungry so that delaying is very difficult (on the level of travelling at night), they wouldn't even have to wait 4 mil.

Chulin 121a - Concept of Achshavei

There is a halacha that is recorded twice in Y.D., once at the end of hilchos sheratzim and once in siman 155 in the Rama - מותר לשרוף שרץ או שאר דבר איסור ולאכלו לרפואה אפילו חולה שאין בו סכנה. The obvious implication is that for the sake for refuah it is permissible to eat a prohibited item that has become inedible, but when it is not being done for refuah purposes, it is forbidden. The Yad Avrohom explains based on the Rosh (2nd Perek of Pesachim) that when one burns chometz before pesach rendering it unfit for consumption, it would still be forbidden to eat on Pesach since by eating it he is giving it importance - מדאכליה אחשביה. Based on this it would be forbidden under normal circumstances to eat a bug or other forbidden item that has been burned, but if it is merely being eaten for medicinal purposes it is permitted since the concept of אחשביה only applies when one is consuming it as a food item. This is to the exclusion of the Sha'agas Aryeh (75) who considers the concept of אחשביה to apply even when one is eating something for medicinal purposes. Either way, the concept of אחשביה is a Rabbinic concept. On a Torah level it would seem impossible for one's intent or purpose to determine an item forbidden or permitted.

However, according to R. Yehuda in the mishna, when one gathers the small pieces of meat that are attached to the inner side of the hide together to make a kezayis, it would have status of a kezyais neveila. Rav Huna explains that this is only when he himself gathers them together, indicating through his actions that he is considering it to be important - דאחשביה וגלי דעתיה דלא בטליה מעיקרא: רש"י. Rashi writes that the concept of אחשביה can be used here, not only in the realm of טומאת נבילה, but even in the realm of איסור נבילה. Meaning, his intent to consider the scraps to be meat restores their status even in the world of issur. Tosafos asks on Rashi, where do we ever find that intent could be the determining factor as to whether a food item is permitted or prohibited!? This would seem to be a machlokes between Rashi and Tosafos whether the concept of אחשביה can even work on a d'oraysa level in the realm of issur v'heter.

The gemara on 120a said that חלב -animal fat that had been liquefied should not be included in the prohibition of eating חלב since it would be drinking and not eating, and we need a special source in the Torah to include it. However, the gemara says that blood which the torah forbids as an issur to eat in it's natural state (as a liquid) would also be forbidden if it were congealed - כיון דאקפיה אחשובה אחשביה - since he gave it status through the act of congealing it. This gemara seems to support Rashi, because we are using the concept of אחשביה to maintain the issur of consuming blood even when it is in solid form. But, upon further analysis, we can ask a more basic question. Why does the gemara require this rationale and not simply state that if liquid blood qualifies as eating, then certainly solid blood would qualify? It seems to me that the gemara is bothered by another issue. Since blood is naturally in a liquid state, consuming it in it's solid state could be considered שלא כדרך אכילה - not the normal way of eating. The gemara is saying that since he congeals it for the purpose of eating it as a solid, it is still considered a normal way of eating. We aren't using this rationale to transform the status of the blood from issur to heter, only to say that it still qualifies as a normal way of eating.

Chulin 116b - Keiva as Rennet

The mishna speaks about "keiva" which refers to the enzymes that line the stomach wall of the animal, and the "or ha'keiva" - skin of the keiva, which is the actual piece of the stomach wall. The keiva is considered merely "pirsha" and therefore concludes that even the enzymes that line the stomach of a neveila or treifa animal can be used, but one cannot use as rennet the actual wall of the stomach of a neveila animal.

Rashi discusses milk that is found in the keiva of the animal that is then salted together with the stomach of the animal. Rashi points out that to permit using this milk that was salted with the stomach as rennet, we would have to assume that the milk found in the stomach qualifies as "pirsha" similar to the enzymes. Rashi rejects this notion and considers the milk to be actual milk so that when salted with the meat of the stomach qualifies as meat salted with milk and becomes assur m'drabonon as bassar b'cholov. We would then say that חתיכה נעשה נבילה so that all that milk has status of issur and when used as rennet will spread issur to all the milk since we say min b'mino is not batul (this is rashi's opinion 109a and many other places that we pasken min b'mino isn't batul. tosafos disagrees and holds that we pasken min b'mino is batul - but in this case where it is effective in being ma'amid the cheese, even tosafos would agree that we don't say bitul).

Rashi implies that had we considered the milk inside the stomach to be merely "pirsha", we would be able to compare this case to fish that was placed in a meat dish, which can be eaten with milk using the concept of נ"ט בר נ"ט, meaning a second generational no'sein ta'am. Both the Rashash on Rashi and the Shach (y.d. 87, 31) point out that even if we were to consider the milk that was salted with the stomach lining to be "pirsha" it would still not be comparable to the hot fish on a meat plate that can be eaten with a dairy food. The concept of נ"ט בר נ"ט  only applies when the second generation flavor stand alone as a permitted entity that you are now going to use with milk. However, when the milk is salted with the skin of the stomach, the "pareve" milk inside the stomach absorbs a ta'am rishon of meat. We then take that ta'am rishon and mix it with milk to create cheese. Since the ta'am sheini of meat is immediately mixing with milk, we consider that to be an issur. Rashi writes that he originally thought that the milk in the stomach qualified as pirsha and was matir, implying that he holds that if the milk were truly pareve because it was considered to be "pirsha" then we could compare it to the case of hot fish in a fleishig plate that could be eaten with milk, and doesn't seem concerned with the aforementioned distinction. 

Rashi 111b (d.h. nosein ta'am) writes explicitly that one cannot put hot milk in a fleishig bowl because the second generation flavor of meat is going directly and immediately into the milk. The case here, even if we consider the milk in the stomach to be "pirsha" should be exactly identical to the milk being put in a fleishig plate where Rashi himself holds that it becomes assur!

Chulin 115a - kol she'tavti le'cha

Rav Ashi says that the source for meat and milk being prohibited to eat and benefit from is the pasuk which says לא תאכל כל תועבה from which chazal darshen כל שתעבתי לך הרי הוא בבל תאכל. The gemara suggests that the same problem should apply to food cooked on shabbos, and it should be prohibited to eat and benefit from, but darshens from the pasuk of כי קדש היא לכם that ma'aseh shabbos is permitted. The gemara further tries to suggest that when one violates the prohibition of plowing with an ox and mule together or muzzling while working, the product should be forbidden. The gemara answers that since we permit ma'aseh shabbos, we should certainly permit the products of plowing with an ox and mule, or muzzling it while working. Rashi struggles with an obvious question, why wouldn't we also learn from ma'aseh shabbos that even bassar b'cholov should be permitted to derive benefit from. Rashi explains that there is a difference. When it comes to meat and milk, one is eating the actual issur that the Torah despised, whereas by ma'aseh shabbos and these other aveiros, we are merely speaking about the product of the issur, not the issur itself.

Tosasfos (end of d.h. choreish) struggles with why we consider the food cooked on shabbos to be merely the product of the aveira but not the תועבה itself, whereas by meat and milk we consider the food to be the actual תועבה that was despised by the Torah? Tosafos explains that it must have to do with how apparent the issur is within the item. By meat and milk where the issur is apparent in the product, the product of the aveira is considered the תועבה, but by ma'aseh shabbos where the issur isn't apparent in the product because one cannot tell from the product that it was cooked on shabbos, the food isn't considered the תועבה.

Tosafos approach seems to be using a d'rabbonon style logic to distinguish between bassar b'cholov and ma'aseh shabbos on a Torah level. It would seem difficult to say that appearance of the product would determine whether the Torah renders it a תועבה. The Rashash suggests another distinction to answer Tosafos question. The cooking of meat and milk is that act of prohibition that the Torah forbids, therefore the product of that act is considered a תועבה. But by ma'aseh shabbos the Torah doesn't forbid specifically the cooking of food, rather the Torah forbids any melacha to be done on shabbos. The food that is cooked on shabbos is not a direct product of what is specifically forbidden by the Torah, therefore not considered a תועבה.

I would like to suggest a slightly different approach. According to the approach that meat and milk that have been cooked together are forbidden to eat and benefit from because they are considered a  תועבה due to the fact that an issur was done with them, it should only be forbidden if cooked by a Jewish adult. Had the cooking been done by a child or at least by a goy, where there was no violation in the process of cooking the product shouldn't be considered a תועבה. Yet, Rashi 114b writes that even if cooked by a goy or a child (rashi implies that we don't render an aveira done by a child to be a ma'aseh aveira), we would consider the product a תועבה. Rashi 114b explains that it is not the act of the aveira that renders the product a תועבה, rather the תועבה is the item itself. Rashi understands that it is as if the Torah would have said that meat and milk is a תועבה, therefore stay away from cooking it. When the Torah identifies an item and forbids an action associated with that item, it can be understood that the action doesn't cause the item to be forbidden, rather the torah recognizes the item as something despised herefore forbids the action i.e. cooking. This would only apply when there is a specific item referred to by the Torah such as meat and milk. The Torah considers meat and milk that is cooked together to be a תועבה, therefore forbids any Jew from cooking it. But, even if a goy were to cook it, the item is still a תועבה. In contrast to the issur of ma'aseh shabbos - the Torah doesn't despise the product, therefore forbid the action of cooking. If that were the case then even something cooked by a goy should be included. The fact that it is only considered ma'aseh shabbos when done by a Jew indicates that the action is what is considered forbidden, and the food is merely a product of the forbidden action to cook. This would not give the food a status of תועבה.

Chulin 114a - Is it Forbidden to Benefit from McDonalds?

According to Shmuel there is an extra pasuk to teach that the issur of meat and milk is binding even on top of a preexisting issur of neveila, therefore one who eats neveila cooked in milk would receive lashes. However, the gemara cites an argument between R. Ami and R. Asi limiting the discussion to be whether one who cooks neveila with milk would receive lashes for the act of cooking, but all agree that since the eating is already forbidden due to the issur of neveila, the prohibition to eat meat and milk isn't binding on top of the preexisting prohibition of neveila.

Based on this, the Rambam (machalos assuros 9) paskens that one who cooks neveila with milk would receive lashes for cooking meat and milk, but one who eats it wouldn't receive lashes for eating meat and milk. However, both the gemara and the Rambam (in mishne torah) are silent regarding the prohibition to benefit from meat and milk. Would that be similar to eating and not apply to neveila, or would it be compared to cooking and apply to neveila?

The Dagul M'rvava (y.d. 87) cited by the Pischei Teshuva (6) quotes the Rambam in his commentary to the mishnayos on krisus who suggests that benefit and eating go hand in hand. Since the issur to eat meat and milk isn't binding on top of the prohibition of neveila, the prohibition to benefit is also not binding. The Pischei Teshuva quotes in the name of the kanfei yona who disagrees with the dagul m'ravava, and the Chasam Sofer who says that one who relies on the dagul m'rvava can't be rejected, but in his opinion the kanfei yona is more correct.

The source of the dagul m'rvava is the Rambam in what he refers to as a נקודה נפלאה in his commentary on krisus. The Rambam asks that the issur to eat basar b'chalav should be binding on the issur of neveila since it is an איסור מוסיף by virtue of the fact that meat and milk is forbidden even to derive benefit from. To this the Rambam says that the issur to eat and the issur to benefit aren't independent entities, rather the prohibition to benefit is an extension of the issur to eat (we see a similar concept in succah 35a by an esrog that is forbidden to eat where rashi writes that it doesn't qualify as לכם. Rashi explains that "lachem" implies that you can benefit from it in all ways - an esrog that is forbidden to eat is missing a major source of benefit). Based on this Rambam, the issur to benefit isn't considered a new issur to cause the issur achila to be binding, and the dagul m'rvava therefore proves from here that even the issur to benefit itself wouldn't be binding. There is a lot of discussion about this Rambam because he seems to say that the approach only works because there isn't an independent source to forbid benefiting from meat and milk, yet in sefer hamitzvos he writes himself that the third repetition of לא תבשל גדי בחלב אמו is an independent source to forbid benefit.

Chulin 103b - Rules of Eating to violate Eiver Min Hachai

The gemara (according to Rashi) has two versions of R. Yochanan as to whether the concept of כדי אכילת פרס applies to אבר מן החי, like it would by all other issurim. On the top of the page the gemara assumed that it would not apply, and on the bottom of the page when it deals with eating a half kezayis and then another half kezayis, assumes that it does.The rationale that אבר מן החי would be different and not have this halacha l'moshe misinai is that even inedible foods combine to the shiur of kezayis. Since אבר מן החי is a chiddush, the halacha l'moshe misinai that allows us to combine all eating within כדי אכילת פרס wouldn't apply to a chiddush case. Without the concept of כדי אכילת פרס the gemara assumes that the entire kezayis must be consumed בבת אחת, but then enters a discussion as to what would qualify as בבת אחת - at one time.

There seem to be three opinions in the gemara what would qualify as בבת אחת, and is dependent on the definition of אכילה. R. Yochanan considers eating to be a function of הנאת גרונו - the mouth. Reish Lakish considers eating to be a function of הנאת מעיו - the stomach. Therefore, R. Yochanan will say that as long as there is a kezayis in the mouth at one time, it is considered בבת אחת, whereas Reish Lakish will say that a kezayis must be swallowed at one time (Rashi explains that it is not possible to chew a kezayis and swallow it all at once since it will naturally begin to slip down his throat, so the only way to swallow a full kezayis would be without chewing. Rashi also seems to hold that swallowing something which is normal to chew wouldn't constitute דרך אכילה, therefore the gemara is forced to make the case of גרומיתא זעירתא which is normal to be swallowed without chewing).

Within the opinion of R. Yochanan that it only qualifies as בבת אחת if a kezayis enters the mouth at the same time, Rashi and Tosafos argue whether we require the kezayis to literally be one unit when it is put into the mouth (tosafos), or whether it can be cut in half so long as there will be a full kezayis in the mouth at one time (rashi). Similarly, they will argue in the opinion of Reish Lakish. Rashi should only require a kezayis in the stomach at the same time, even if it were swallowed in parts (this is actually tosafos question on rashi because reish lakish seems to hold that a full unit of kezayis must be swallowed at one time), whereas Tosafos requires a full unit of a kezayis to be swallowed at one time.

However, according to R. Elazar both Rashi and Tosafos would agree that if one would eat a half kezayis and after a slight pause eat another half, it would qualify as an eating בבת אחת to be chayev. The concept of כדי אכילת פרס would have only permitted the pause to be longer between the two half kezaysim. Since we don't apply כדי אכילת פרס, the pause must be very slight - רש"י - שנתרחקו זה מזה מעט.

The Rambam (Ma'achalos Ha'asuros 5:3-4) has a very different approach in this gemara. Firstly, the Rambam understands that the case of חלקו מבחוץ is not when one eats a half kezayis and then another half kezayis as rashi says, nor is it a case where one splits the kezayis in half and puts both halves in his mouth together as Tosafos says. Rather, the case is where he separates the meat from the bone so that it is no longer one unit. The Rambam understands that the chiddush ha'torah which allows you to combine the bones to make up the kezayis only applies when the integrity of the limb is maintained. As soon as one separates the meat from the bone, the bones are no different than bones by other issurim which don't qualify as an eating. Therefore, the case of חלקו מבפנים that you are going to be chayev is when one puts the meat in his mouth with the bone, and only in his mouth do they separate from one another. Since they were placed in his mouth together, they combine.

The Rambam also holds that paskening like R. Elazar wouldn't undermine the assumption of R. Yochanan. R. Elazar who allows one to be chayev even if they would break the eiver into pieces and eat a half kezayis and then another half, would only apply if ultimately he ate a full kezayis of MEAT. Therefore, if he actually ate a full kezayis of meat, he is chayev even though he separated the meat from the bone and ate it little by little (even with slight pause in between) which is the halacha of R. Elazar. But, in order to combine the bones with the meat to fill the shiur of kezayis, he must place the bone in his mouth together with the meat and together they must make up a kezayis - which is the halacha of R. Yochanan. In other words, the Rambam understands that R. Elazar takes issue with the definition of eating בבת אחת that R. Yochanan establishes by relaxing the requirement of putting it in one's mouth together (when there is no need for bones to be considered toward the kezayis), but agrees with the din of when bones can be combined - only when they are together with the meat at the time they are consumed.

Chulin 102a - Eiver Min Ha'chai

The gemara says that even though the prohibition of אבר מן החי for a Jew may only apply to kosher animals (acc. to chachamim and R. Meir), for a goy it will apply even to non-kosher animals. Tosafos 33a questions how this can be. Wouldn't this be a violation of the rule that there is nothing prohibited to a goy that is permitted to a Jew - ליכא מדעם דלישראל שרי ולעכו"ם אסור. Tosafos says that since there would be a prohibition for the Jew to eat a non-kosher animal, even though it wouldn't be considered אבר מן החי, it would not violate the principle of something being permitted to a Jew and prohibited to a goy. Tosafos holds that the prohibition on the goy doesn't have to be the same prohibition on the Jew so long as there is some prohibition (R. Akiva Eiger in a teshuva 165 qualifies this idea and says that it would only be when the prohibition on the Jew is a lack of shechita such as a non-kosher animal, to the exclusion of a treifa where it has already been shechted properly and has not relation to the issur of eiver min ha'chai).

It seems to me that Rashi in our sugya is also addressing the same question. Rashi writes -

אבל בן נח מוזהר על הכל, דכל דקרינא ביה בשר לחודיה אכול, קרינא ביה אבר מן החי לא תאכל. Rashi says that whenever it is permitted to eat the meat after being killed, there is an issur of eiver min ha'chai to eat the meat prematurely. Perhaps rashi understands that the principle of there is nothing prohibited to a goy that is permitted to a Jew isn't violated here because the same exact principle that applies to the goy - don't eat alive what you can eat dead, applies to the Jew. The only difference is that the Jew cannot eat non-kosher animals when dead so there is not issur of אבר מן החי when it's alive, but for the goy there is. Since the principle applies equally to the Jew and goy it wouldn't violate the rule of ליכא מדעם דלישראל שרי ולעכו"ם אסור.

Chulin 101b - The Two Prohibitions of Yom Kippur

Rashi explains that when the gemara tries to prove that R. Yossi Haglili holds of איסור כולל from the fact that when yom kippur falls on shabbos and he does melacha he has to bring a korban both for shabbos and for yom kippur. Even though YK and shabbos are entering at the same time, one can only be liable for both since if theoretically one would start before the other, each can be binding on top of the first. Rashi explains that even if shabbos would enter prior to YK, the prohibition of YK would be binding on top of shabbos as an איסור כולל. The fact that YK forbids not only doing melacha, but also eating and drinking makes it an איסור כולל to allow the prohibition of melacha to be binding on top of the prohibition against doing melacha on shabbos - מיגו דאיתסר באכילה משום יוה"כ איתסר ליה נמי מלאכה משום יוה"כ. The difficulty of this rashi is how can we say an איסור כולל from the issur to eat to the issur to do melacha, they are totally separate prohibitions. From rashi we learn a new approach in understanding the nature of the issur to eat and to do melacha on YK. Although in the counting of mitzvos they are completely independent, and would seemingly be two completely separate prohibitions that apply on the 10th of Tishrei, that is not how rashi is viewing it. Rather, the kedusha of YK results in two halachos, one is a prohibition of eating and the second is the prohibition of melacha. Both are outgrowths of the kedushas ha'yom and not independent prohibition that apply to the calendar date of 10th of Tishrei. It would now make sense that Rashi can consider YK in the general sense to be an איסור כולל from eating to melacha, since both are merely outgrowths of the kedusha of YK.

I would like to suggest that the Rambam would not agree with rashi. Rambam (Hil. Shevisas Asor 1:6) writes that the mitzvah d'oraysa to add to YK before and after is limited to YK (not shabbos and yom tov) and limited to the עינוי of YK, it doesn't extend m'doraysa to the issur melacha. The Minchas Chinuch clearly understands the Rambam this way. The Rambam would seem to hold that m'doraysa when one is me'kabel YK early, they are prohibited from eating but not prohibited from doing melacha. The fact that by accepting kedushas ha'yom one can be prohibited from eating but not from melacha implies that the they are not an outgrowth of the kedushas ha'yom, rather two independent halachos that apply on the 10th of Tishrei and could theoretically exist one without the other.

Chulin 99b - Bitul in more that 60x

The Rama (y.d. 98) writes that foods with a very strong flavor such as spices are not batul in 60x because the flavor is still able to be tasted, however the Rama limits this to when the item is prohibited in and of itself (i.e. teruma or avoda zara), to the exclusion of spices that just have a non-kosher item absorbed in it. The source for the Rama is our gemara where we see that "grissin" which fall into lentils can give flavor even if there is 100x as much to be mevatel. Clearly, the idea of 60x is an assumption but doesn't apply to cases where the flavor is actually tasted. But, regarding the Rama's stipulation that this rule would not apply to foods that have the taste of issur absorbed in them, but are not assur themselves, the Gr"a quotes those who disagree. The Gr"a writes that in our gemara we find that fish brine isn't going to be batul until there is 192x as much, even though the actual water and vinegar in the brine isn't technically assur, just that it has the flavor of the fish fat absorbed inside of it. The same should apply to a spice which has the flavor of non-kosher meat - so long as the spice could be tasted in whatever dish it falls into, it should be assur even if there is 60x as much.

The Shach writes that when spices are able to assur foods even when there is more than 60x, it is only an issur d'rabonon. R. Akiva Eiger quotes the Ran who disagrees and holds that it would be d'oraysa. The Ran is easy to understand, but the Shach is harder to understand - why would it only be d'rabonon? It seems that the Shach understands that once there is 60x of the mutar food to the assur food, the flavor is weakened to a point that it isn't considered true ta'am and therefore it is only assur m'drabonon.

Chulin 99b - Gid Hanashe is Prohibited to Derive Benefit From

The gemara has a discussion in Pesachim about things that are prohibited to eat, whether they should also be prohibited to derive benefit from. Either way, one of the approaches to understand the nature of issurei achila - things that are prohibited to eat, is that it is essentially a prohibition to derive benefit, but the Torah only forbids the epitome of benefit from the item - eating. Meaning, that the nature of issur achila is that it is prohibited to derive the benefit that this item is meant to provide which is the benefit of eating. This would explain for example why we wouldn't consider an achila gassa (over eating), or eating of something which taste bad to be a violation of eating, since there is no pleasure or benefit associated with that eating. 

However, Tosafos makes a calculation in our sugya that undermines this premise. Tosafos proves from the gemara in Pesachim that according to the opinion who considers giddin (sinews) to have flavor, it is only prohibited to eat. But according to the opinion who doesn't consider it to have flavor, it is even prohibited to derive benefit from. Since we rule that Gid Ha'nashe doesn't give off flavor, we must rule that one cannot derive benefit from it - therefore it cannot be gifted to a goy, if the presence of the gid hanashe will raise the stature of the gift. Now, if one were to eat gid hanashe they would certainly be in violation of the prohibition to eat gid hanashe, even though there is no flavor so that they cannot be in violation of the issur to derive benefit. If it were true that the prohibition to eat is a form of deriving benefit, one couldn't be in violation of eating gid hanashe since there is no benefit and would only be in violation on selling or giving to a goy in which there is benefit. The fact that one is in violation even for the eating of gid hanashe which has no flavor, indicates that eating is in no way contingent on the pleasure or benefit one receives from the food, rather it is an act that the Torah forbids regardless of the benefit it provides.

Chulin 94b - Rules of Geneivas Da'as

The gemara on amud alef has three answers to explain the mishna. Tosafos writes that according to the first answer of the gemara that the mishna is speaking in a place where they call out so it is permitted to purchase from a goy, the mishna would contradict the braisa. To reconcile the contradiction Tosafos is forced to distinguish between a sale and a gift - only by a sale where money is being paid is there an issur of g'neivas da'as. However, according to the second and third answer Tosafos says that only when you explicitly lie is it considered g'neivas da'as, but if you just do something where the other party draws his own conclusion it would be considered איהו הוא דקא מטעי נפשיה (as we see in the gemara and isn't considered gneivas da'as). Tosafos modifies this slightly by saying when one does an action that is suggestive such as opening up a barrel of wine in the presence of the guest indicating that it is in his honor, that is tantamount to actually saying that you are doing it for him. Rashi seems to maintain that once the gemara introduces the concept of איהו הוא דקא מטעי נפשיה, we limit ALL the cases of geneivas da'as to where he explicitly told the person that he is doing it for him, or explicitly told the person that it was shechted meat. We see from here that one is not obligated to correct his friends misunderstanding of the situation, but cannot actively mislead him.

Chulin 94a - Geneivas Da'as

The gemara in trying to figure out the p'shat in the mishna that prohibits sending meat from which the gid ha'nashe was removed to a goy, offers a few explanations. The final explanation is that it is a violation of geneivas da'as. Being that the first two answers are able to explain the mishna without inventing a concept of geneivas da'as, perhaps we shouldn't pasken like the approach that relies on this concept. The Rosh takes this approach and rejects the notion of geneivas da'as when one sends a gift to a goy, such as the case in the mishna and limits the problem of geneivas da'as specifically to a sale. With this he is able to work out the various other sources that indicate geneivas da'as is a real prohibition, but rejects applying the concept to the case of the mishna since it was being sent as a gift rather than a sale (עיין במעדני יו"ט ס' ר' שמוכיח מהש"ס שאין חילוק בין מכר למתנה). It would seem from the Rosh's approach that geneivas da'as applies to a sale but not a gift, that it is essentially an offshoot of the prohibition to steal. When one is giving a gift and not receiving anything in return as part of the compensation, it cannot be considered stealing. But, when one is receiving some level of compensation, it is prohibited to fool the buyer since the entire compensation is now being given under a false pretense (even though the buyer may have paid the same price even had he known the truth).

In my opinion there are 3 approaches to the nature of the issur of geneivas da'as. The Rosh holds that it is an offshoot of actual theft. Rashi and the Rambam reject the approach of the Rosh, yet differ in how they portray the issur.

Rashi writes  multiple times in the sugya - ונמצא מחזיק לו טובה חנם. This implies that the prohibition is not stealing the compensation because rashi uses this logic even in the case of a gift where there is no compensation. Rather, the prohibition is not at the time of the geneivas da'as, it is violated afterward when you accept the goodwill of the receiver and his interest in responding in kind for something that he thinks you did for him, when in truth you didn't do for him as much as he thinks you did. It would seem from rashi that if one would notify the goy immediately after the violation of the geneivas da'as before he will have feelings of goodwill, he will avoid the entire prohibition. The issur is not in fooling the goy, nor is it in stealing compensation for the goy, but is is accepting his goodwill.

The Rambam in Hil. Dei'os 2:6 has what would be considered the simplest approach to the nature of geneivas da'as. The Rambam writes

אסור לאדם להנהיג עצמו בדברי חלקות ופיתוי, ולא יהיה אחד בפה ואחד בלב אלא תוכו כברו והענין שבלב הוא הדבר שבפה, ואסור לגנוב דעת הבריות ואפילו דעת הנכרי, כיצד לא ימכור לנכרי בשר נבילה במקום בשר שחוטה, ולא מנעל של מתה במקום מנעל של שחוטה וכו' ואפילו מלה אחת של פתוי ושל גניבת דעת אסור, אלא שפת אמת ורוח נכון ולב טהור מכל עמל והוות

The Rambam considers the prohibition to have nothing to do with the subject of the geneivas da'as. It is a violation of the מידת האמת that is expected of a Jew, and by lying to the anyone, even a goy, he is undermining this essential midah of being truthful. The difference between the Rambam and Rashi is that according to Rashi the prohibition exists because of the outcome of the undeserved goodwill that the Jew will receive from the goy, whereas according to the Rambam the issur is the act of deceiving another human being.

Chulin 89b - Merit of Avrohom Comparing Himself To Dirt and Ash

The gemara says that in the merit of Avrohom Avinu comparing himself to dirt and ash, the Jewish people merited the parah aduma which involves ash and the Sotah which involves dirt. The Maharsha explains that it doesn't mean to say that had Avrohom not made the comment אנכי עפר ואפר, we would never have a way to remove the tu'mah of tu'mas meis and would never have a method for the Sotah would never have a method to return to her husband. Rather, there would have been a far more complex and difficult process to achieve these results. In the merit of Avrohom humbling himself with the statement of אנכי עפר ואפר, they were able to achieve these results in an easier form using mere dirt and ash.

I would add that the attribute that most greatly separates between people is that of arrogance. Humility is an attribute that breeds togetherness. In the merit of Avrohom's humility, we were zocheh to two mitzvos that bring people back together. The ashes of the para aduma allow tamei people to once again interact with the tahor, and the dirt of the sotah allows her back to her husband.

The gemara asks that the mitzvah of כסוי הדם should have also been in the merit of Avrohom comparing himself to dirt.The gemara responds that there has to be a tangible benefit that comes from the mitzvah, and by covering the blood there is no tangible benefit. It seems to me that Rava who is the person making the statement is li'shitaso. We find that Rava himself on 89a takes a position of מצות לאו ליהנות ניתנו, which simply means that the merit of the mitzvah in itself doesn't qualify as a benefit. Only physical benefits qualify as real הנאה. Therefore, Rava holds that the benefit of having a mitzvah to perform thereby an opportunity to receive reward in the world to come, doesn't qualify as a benefit and therefore isn't significant enough to be the reward for Avrohom's statement. It is only the physical and tangible benefit that come from פרה אדומה and עפר סוטה that can be the reward for Avrohom's statement.

As an aside, Rashi says that the ability to eat the meat cannot be considered the "benefit" of כסוי הדם since the kashrus of the meat is not at all dependent on kisuy ha'dam. The Pri Megadim (y.d.sifsei da'as 28:2) says that we cannot prove from here that it is permitted to eat the meat without kisuy ha'dam. Perhaps Rashi means to say that if there wouldn't have been a mitzvah to cover the blood, it would have been permissible to eat the meat, so we can't consider this mitzvah to be a real benefit. However, now that there is a mitzvah to cover the blood, it is entirely plausible that until it is done, the meat cannot be eaten. Nonetheless, l'ma'aseh we assume that the mitzvah of kisuy ha'dam has zero to do with the ability to eat the meat. Even if by tevilas keilim for example, the use of the vessel prior to tevila may be a bitul of the mitzvas aseh, by kisuy ha'dam the kashrus of the meat doesn't seem to be at all connected to the mitzvah on the blood.

Chulin 87a - Paying 10 Gold Coins

The gemara discusses the issue of paying 10 gold coins for robbing someone of their mitzvah. The gemara questions whether a mitzvah containing multiple brachos such as birchas hamazaon is 10 zehuvim per bracha, or 10 for the entire mitvah. Assuming it is per bracha, the gemara assumes the amount for birchas hamazon would be 40. Rashi explains that 10 per bracha, which means that the fourth Rabbinic bracha of ha'tov v'hamei'tiv would also have 10 zehuvim. Tosafos (d.h. v'chayvu) questions when one is called to the Torah and another grabs the aliya whether the latter owes 10 zehuvim. Tosafos offers two arguments why the person who "stole" the aliya wouldn't have to pay: 1. the rights to an aliya belongs to everyone (perhaps this is only when one was supposed to get the aliya, but wasn't yet called up?). 2. Even if a Yisroel stole the aliya of the kohein he wouldn't have to pay because וקדשתו - לכל דבר שבקדושה לפתוח ראשון ולברך ראשון, is only an אסמכת. Tosafos seems to hold that the requirement of וקדשתו is only d'rabonon, and since it's not from the Torah, there isn't any obligation to pay for stealing that right.Yet, in the very next Tosafos they seem to hold that one is required to pay 10 zehuvim for both ha'tov v'hameitiv and borei pri ha'agfen, both of which are only d'rabonon?

To me it seems that Tosafos isn't focusing on whether the mitzvah of וקדשתו  is d'oraysa or d'rabonon. First of all, the magen avrohom (201:4) points out that the gemara in gittin 59b clearly holds that וקדשתו is d'oraysa. Secondly, even if it d'rabonon, there should be a requirement of 10 zehuvim. Tosafos fully agrees that the requirement to give kedusha to the kohein is d'oraysa. However, the Rabbonon came along and gave specific examples in which the kohein must be honored, one of the being the first aliya. But, both the Torah and the Rabbonon never gave this as a right and entitlement of the kohein, rather they demanded of the tzibbur to honor the kohein in this manner. The concept of paying 10 zehuvim is only when one steals a mitzvah that their friend is entitled to, it doesn't apply when one merely fails to fulfill their obligation to that person. Tosafos perhaps understands that had the Torah been referring specifically and directly to giving a kohein the first aliya, it would be understood not just as an obligation of the tzibbur but an inherent right of the kohein granted to him by the Torah, and if stolen from him he would be owed 10 zehuvim. But, since the specifics were only introduced by the Rabbonon, it is not an inherent right, rather they placed an obligation on the tzibbur. Therefore, even when the tzibbur fails to fulfill their obligation, no one would owe money to the kohein.

Chulin 86a - Difference Between the Mitzvah of Covering Blood and Shechting Mother and Child On Same Day

The simple reading of the mishna implies that both R. Meir and Chachamim agree that the shechita of a child is invalid so that there is no requirement to cover the blood, yet in the end of the mishna the Chachamim hold that if a חרש שוטה וקטן shechts the mother, one cannot shecht the child on the same day because we are concerned that the shechita is actually valid. The gemara discusses why the Chachamim would be more strict to forbid shechting the child on the same day than with the mitzvah of covering the blood, and ultimately cannot come up with any rationale. This forces the gemara to conclude that the Chachamim would indeed argue by the mitzvah of covering the blood as well, and would require the blood to be covered after the shechita of a חרש שוטה וקטן. Tosafos raises a very interesting question. There seems to be a very obvious distinction between the mitzvah of covering the blood and the prohibition of shechting mother and child on the same day. It is typical for the Rabbonon to uproot and be passively be mevatel an aseh, a positive mitzvah, in order to preserve a negative commandment and prevent it's violation as they did with shofar on shabbos. Therefore, it is perfectly logical to absolve the shechita of the child from the mitzvah of covering the blood (note: the mitzvah couldn't be on the child, rather on those watching as rashi writes), in order to preserve the prohibition of neveila because if they would require the covering of the blood it would mislead people to thinking that the meat was kosher. However, in the context of אותו ואת בנו, it wouldn't make any sense for the Rabbonon to absolve from the prohibition of אותו ואת בנו and permit the slaughtering of the child in order to preserve the prohibition of neveila. Why would they be more lenient about one negative commandment in order to preserve another? Tosafos suggests that in truth the assumption is that the animal is a neveila and there is no mitzvah of covering the blood and no prohibition to shecht the child. However, being that there is a small chance that their shechita is valid, it would have been worthwhile to cover the blood on the off chance that the shechita was valid. Yet, the Rabbonon didn't want this done because it would mislead to the eating of the animal. Similarly, the gemara asks they should have been concerned that being machmir for not shechting the child (which is not technically a concern since we assume their shechita was invalid), would lead to the eating of the animal (which is really assumed to be assur). That is why the gemara understands that there shouldn't be any distinction between the reisha and seifa of the mishna. It seems to me that Rashi would not be able to use Tosafos answer. Tosafos answer is predicated on the premise that the animal shechted by a חרש שוטה וקטן is really a neveila, not just a safeik and therefore a more real concern than אותו ואת בנו. But, Rashi (ד"ה מאי שנא, וד"ה לחומרא) seems to view it as a regular safeik according to the Rabbonon whether the shechita is valid. Therefore, Tosafos question comes back. It seems to me that the rationale as to why the gemara felt it would make sense to be more concerned with the safeik of neveila, than with the safeik of אותו ואת בנו, is because if we were to do something that would indicate the neveila was permitted to eat (such as cover the blood or abstain from shechting the child that day), one would definitely eat the neveila. There would be no question that one would not want to waste meat that seemed permitted and would definitely use it, therefore by permitting neveila it would unquestionably lead to the issur. Whereas saying that one may shecht the child on the same day will not definitely lead to an issur, since the owner would only shecht it if he actually needs it. Therefore, it would make sense for chazal to ignore the issur of אותו ואת בנו if by being concerned for it would lead to the violation of eating neveila.

Chulin 85a - CARRYING SHOFAR FOR WOMEN

The gemara uses shofar as a pircha to the kal v'chomer of rav yossi. The logic is that shofar is an example of something which doesnt push off shabbos even if it is a definite obligation, yet the safeik mitzvah such as a tumtum who is a safeik woman, can blow on yom tov. The point of the gemara is to show that yom tov is less severe than shabbos. However, the gemara never clarifies what actual prohibition we are speakingmes to shofar on yom tov. Tosafos offers 2 suggestions: 1. The prohibition being discussed is the issur of carrying. Since women aren't obligated in shofar it should be prohibited to carry for them. Yet, a tumtum who may be a man and may be fully obligated, can carry a shofar. 2. The issue being discussed is merely an ussur d'rabonon of carrying on yom tov. According to the first approach, the shares aryeh 106 proves that a shofar cannot be carried to the public domain on yt for the sake of a woman. This is also the.implication of tosafos at the end of the sugya who implies that similar to semicha, only an issur d'rabonon can be done, not carrying which is doraysa. Rav Moshe (oc 3:94) has a very long and complicated teshuva arguing on the shaagas aryeh and proving that a shofar or lulav can even be carried on yt where there is no eiruv to enable a woman to do the mitzvah.

Chulin 82a - Hazmana Milsa

R. Akiva Eiger writes in a Teshuva (3) that the issue of whether by something that actually has kedusha i.e. the klaf of a sefer Torah, we say that setting aside is significant and makes it assur even before it is used, is dependent on a machlokes in our gemara. According to Rav Yanai who says that sending down the eglah arufa to nachal eisan makes it assur, the same would be true with anything that is inherently an item of kedusha - הזמנה מילתא היא. But, according to those who say that it would only be assur by the shechita, they would have to hold that even by something which is an actual גוף הקדושה (not just תשמישי קדושה), the הזמנה would not be significant enough to create an issur.

The gemara says that according to the opinion who says that by eglah arufa the sending it down to nachal eisan makes it assur, by the birds of the metzorah the purchasing of the birds for the use of the metzorah would make it assur. Rashi explains how we can compare the purchasing of the birds to the sending of the calf to nachal eisan, we should compare the purchasing of the birds or initial taking for metzorah purposes with the purchasing or initial taking of the calf. Rashi explains that by egla arufa where there is a later act prior to shechita to be considered the designation of it and create the issur, we assume that act is what creates the issur. But by the birds where there is no later act, the purchasing or taking is considered the act that creates the issur. The difficulty with this in light of R. Akiva Eiger is that if we are really dealing with an issur of הזמנה מילתא היא, we should consider the very first act of designation to be hazmana, not the very last act before shechita such as the sending down to nachal eisan.

Chulin 81a - Nituk L'aseh

The gemara says that the la'av of לא ירצה which says that you can't be makriv an animal with a mum and the gemara darshened that it should include anything which is not fit to be makriv, wouldn't include a מחוסר זמן. Meaning, an animal that is premature such as before 8 days old, or אותו ואת בנו which is also considered premature, the torah is menatek l'aseh. Tosafos understands simply that the gemara means that the aseh pulls it out of the category of the la'av entirely so that one cannot be in violation of לא ירצה by being makriv an animal that is מחוסר זמן. However, Rashi seems to understand that the language of נתקו לעשה is using the standard mechanics of a לאו שניתק לעשה where the halacha is that you certainly violated the la'av but there is no malkus. The difference between rashi and tosafos is when one is makriv an animal that is מחוסר זמן, did he violate the la'av of  לא ירצה - according to rashi he did, but according to tosafos he didn't. Tosafos asks on Rashi that this doesn't seem to follow the normal setup of a לאו שניתק לעשה. Normally it means that one can do something to fix up the la'av after violating the aseh such as returning the stolen goods or sending away the mother bird. Here, once you are makriv the animal prematurely (or on the same day as it's mother), there is nothing to do to fix it up. The aseh is something that should have been done instead of violating the la'av but doesn't help to "fix" the la'av. To explain Rashi's position it seems that rashi holds that a לאו הניתק לעשה doesn't have to be something active, rather it is a technicality of how the Torah presents the la'av. Rashi understands that when the Torah presents the la'av as something that can only be done after the aseh, it is a לאו שקדמו עשה and doesn't qualify as a לאו שניתק לעשה, therefore you would get malkus. But, whenever the aseh only exists after the la'av even though it doesn't fix the la'av (because once the la'av is violated, there is no ability to do the aseh), the Torah is indicating that there is no malkus for the violation of the la'av. This approach works in Rashi in our sugya and would answer the question that Tosafos has, but doesn't work in the sugya in makos of בטלו ולא בטלו  and קיימו ולא קיימו which focus very much on the ability or inability to fulfill the aseh after the violation of the la'av.

Chulin 79b - Equating Simanim of a Mule to that of a Lost Object

The gemara says that R. Abba demanded that when two mules are tied to a wagon, they must both have a mother who is a horse and father who is a donkey, or the reverse. But if one would have a mother who is a donkey and the other a mother who is a horse it would be an issur of kelaim since we are machmir for the opinion of R. Yehuda who holds that we disregard the father and consider the child to be the species of the mother. However, R. Abba allowed them to figure out the species of the mother using the simanim of a short tale and long ears being indicative of a mother who is a donkey, and the opposite being indicative of a mother who is a horse. The gemara comments that his willingness to rely on these simanin indicate that he holds simanim are d'oraysa because otherwise he couldn't rely on them for kelayim which is essentially an issur d'oraysa. Rashi comments that whether simanim are indeed d'oraysa is a discussion in baba metziah and R. Abba would be holding that they are d'oraysa.

The Ramban asks that Rashi's connection to the gemara in Baba Metzia regarding identification of either an object or a dead husband, doesn't seem to be at all related to simanim in this context. The issue of using simanim of identification and questioning whether they are "d'oraysa" is because they aren't 100% conclusive since it is possible that another object may possess these simanim as well (whereas a siman muvhak that is conclusive is certainly d'oraysa). However, in our context chazal seemed to have a tradition that every child born from a mother donkey will have a short tail and long ears, and every child born from a mother horse will have a long tail and short ears. To rely on simanim in our context because they are d'oraysa, meaning a tradition from moshe m'sinai that they can be relied on for kelayim, wouldn't be any indication of simanim being d'oraysa when used as identification of an object or person.

It seems that the connection of Rashi forces us to say that the simanim used to identify whether the mother is a donkey or a horse are not a tradition from Moshe Mi'Sinai. Rather, Chazal must have noticed that statistically speaking one could safely assume that when the mule possesses simanim in the ears and tail of a donkey, it's mother is a donkey, and if it possesses simanim of a horse, it's mother is a horse. These aren't absolute, rather statistically correct. Therefore, Rashi holds that the simanim in our context are also identification type simanim rather than being absolute indicators of the species of the mother.

Chulin 78a - Aseh Pushing Off Lo Ta'aseh and Aseh

The gemara has a rule in many places that although a positive mitzvah (aseh) can push off a negative mitzvah (lo ta'aseh), anytime a mitzvah has a lo ta'aseh and an aseh we don't allow another aseh to push off both the negative and positive mitzvah. The example is the mitzvah of covering the blood of a bird when it's shechted where there is an aseh to cover the blood, but if done on yom tov it would violate an aseh and lo ta'aseh, so we don't allow one to do the mitzvah of covering the blood on yom tov.

However, the question is raised whenever we have a situation of aseh trying to push off aseh and lo ta'aseh, whether we allow the aseh to push off the lo ta'aseh just not the supporting aseh, or do we say that since the aseh can't push off the opposing aseh, it also can't push off the opposing lo ta'aseh. The Riva quoted by Tosafos in Chulin 141a holds that in a situation where there is an aseh opposing a lo ta'aseh and and aseh, if one would fulfill the aseh thereby violating the lo ta'aseh and aseh, they would not get lashes for the violation of the lo ta'aseh because the aseh effectively pushed off the lo ta'aseh, just isn't powerful enough to push off the opposing aseh. In my sefer, Nasiach B'chukecha (page 214) I discussed this issue and showed how it is a machlokes rishonim. In the additions to my sefer, I pointed out that Tosafos on today's daf seems to disagree with the Riva and holds that when we have an aseh up against a lo ta'aseh and an aseh, it would not even push off the lo ta'aseh so that if it is violated there would even be malkus for the violation.

Tosafos D.H. Minayin, asks why do we need a source to teach that the prohibition of shechting a mother and child on the same day would apply to kodshim, the fact that it would be written without any qualification would automatically make it apply to kodshim? Tosafos suggests that perhaps we need the pasuk to say that even if there is a mitzvah that must be done with this animal such as korban pesach, you cannot shecht it if the mother has been shechted earlier that day. Meaning, without a special source we would allow the mitzvah of Korban Pesach to push off the prohibition, but now that we have a source that it applies to kodshim we wouldn't allow the mechanics of aseh pushing off a lo ta'aseh to take place. Tosafos rejects this answer because shechting a child the same day as the mother would be a violation of both an aseh and a lo ta'aseh so even without a special source we would never have allowed the aseh of korban pesach to push off both an aseh and a lo ta'aseh that forbids shechting the mother and child on the same day. Tosafos seems to understand that whether we had a special pasuk declaring that one cannot shecht the child on the same day as the mother to fulfill the mitzvah of korban pesach, or didn't have a special pasuk, the result would be the same since the rule of אין עשה דוחה לא תעשה ועשה wouldn't allow the violation. Now, if the Riva is correct that when we have a situation of אין עשה דוחה ל"ת ועשה we wouldn't give lashes for the violation because the aseh would indeed push off the lo ta'aseh, just not the supporting aseh, then we would still require a pasuk to say that the issur of אותו ואת בנו doesn't apply to kodshim. Without a special pasuk, if one were to shecht the child the same day as the mother, he wouldn't get malkus. Now that we have a special pasuk teaching that even by kodshim animals that are needed for a korban the prohibition applies, there would be malkus for the violation. The fact that Tosafos maintains that the rule of אין עשה דוחה ל"ת ועשה is sufficient even without a special pasuk, implies that the rule of אין עשה דוחה ל"ת ועשה alone would also allow us to give lashes to one who violates, which is against the Rivah.

Chulin 74a - Dangling Limb

The Gemara concludes that when one shechts an animal with a dangling limb, the shechita is effective on the limb on a Torah level both to prevent it from having an issur status of neveila (or eiver min ha'chai) and to prevent a tu'mah status of neveila. The Rabbonon imposed a rabbinic prohibition against eating it, but didn't impose any tu'mah status. The Rambam (Hilchos Ma'achalos Asuros 5:6) in codifying this halacha writes that the status of a dangling limb on an animal that was shechted is that it is assur but there is no malkus (if it died by itself, it has a status of eiver min ha'chai both for issur and for tu'mah). It is unclear from the language of the Rambam אסור ואין לוקין עליו whether he means to say that it is an issur d'rabonon or an issur d'oraysa just that there is no malkus. The Pri Chadash (Y.D. 62) explains that according to the Rambam it is an issur d'oraysa but since ultimately included in the לאו שבכללות of בשר בשדה טרפה (as the gemara says 73b), there is no malkus. The Maharatz Chiyus quotes that the Pri Chadash proves this from the Tosefta that says that a dangling limb is assur for Goyim. Generally speaking we don't find Rabbinic prohibitions on Goyim, therefore the fact that it is considered אבר מן החי even for a Goy implies that it is an issur d'oraysa.

Chulin 73a - Long Handles on Keilim

The gemara explains the position of R. Meir who holds that vessels with long handles only require tevila up until the point that the handle serves a function but not beyond that point. The rationale is that since it will be cut off, we view it as if it were already cut off and therefore isn't part of the vessel. The Rosh and Rash in Keilim develop from this mishna an interesting principle. Normally, areas that qualify as beis ha'starim on a person we don't require water to actually touch so long as there is no chatzitza rendering the area fit for water to enter. However, if that were the halacha by keilim as well it wouldn't make sense to simply be tovel the vessel until the point where the handle will be cut, because the point at which it is cut is not fit for bi'as mayim - to touch the water. Clearly, the halacha of beis has'tarim of vessels is that it doesn't even need to be fit for water to touch. However, the Mishna Acrhona (one of the commentaries in taharos) disagrees. He holds that even by keilim there is a requirement that the beis hastarim be ראוי לביאת מים, yet we don't consider the area that would be exposed when it is cut to be a problem because it is the minority of the vessel and people aren't makpid about the handle being there, therefore it isn't a chatzitzah. In truth, Tosafos (d.h. matbil) also considers the handle prior to being cut off to be a problem of chatzitza at the point that it will be cut and therefore makes the case where water can permeate the handle so that it isn't a chatzitzah. See Mayim Rabim pg. 236.