Temurah 14b - Reciting written Torah by heart

The gemara says that oral torah cannot be written, and written torah cannot be recited by heart. It compares one who writes halachos to one who burns a sefer torah. Rashi explains that if a fire would break out on shabbos it would be forbidden to violate shabbos to save the sefer of halachos, therefore the initial writing of it causes it to be burned. Rashi offers a second interpretation that it is destructive to the oral Torah to commit it to writing. The second explanation is difficult, why is it equivalent to burning of a Torah? It seems that the problem with writing oral torah is that it make what should be infinite into something limited and finite. Therefore, by writing halachos one is inherently considering it to be no longer disputable and no longer open for debate. He is "burning" the torah that could have been discussed and introduced on this topic by committing the torah to writing. The exception to this rule the gemara says is when one writes a chiddush that presumably would otherwise be forgotten. The writing of a chiddush is necessary for the preservation of torah and therefore wouldn't be a violation of writing what shouldn't be written.

Similarly, one is not allowed to read the written torah by heart. Tosafos asks from various written sections of the Torah that were accustomed to being recited by heart in the context of davening. Tosafos answers that it is only problematic when one recites a written section by heart with the intent of being motzi someone in their obligation i.e. reading krias shema for someone who is going to be yotzei through sho'meia k'oneh. Tosafos also limits the violation to chumash as opposed to nevi'im and kesuvim.

The Shulchan Aruch (O.C. 49) says that sections which people are familiar with such as shema and birchas kohanim one is allowed to do by heart, but doesn't quote Tosafos who permits anything which is not being done to be motzi others. The rationale of the Shulchan Aruch seems to assume that the problem is that we afraid of one making an error and misquoting from torah she'bichsav, therefore things which are well known are permitted. This is also the implication of the biur halacha citing Tosafos Yeshanim to permit reciting hallel by heart. However, the limitation of Tosafos to when one is being motzi others seems to be that when done casually and not to be motzi someone's obligation, it isn't significant enough to qualify as a prohibition.

The Mishna Berura uses Tosafos as cited by the Gr"a and Radvaz to permit one to read the parsha along with the ba'al koreih even though they don't have a chumash open in front of them. The M.B. also quotes from the chavos ya'ir to permit one to recite tehillim by heart combining the heter of the chavos ya'ir that it qualifies as tefilla and the heter of tosafos that one isn't being motzi others. It is interesting that they don't quote the other distinction of tosafos who limits the prohibition to chumash.

Temurah 8a - Not to sell a bechor or ma'aser in the market

The Mishna in Bechoros 31a says that one is not allowed to sell the meat of a bechor or ma'aser b'heima on the regular meat market because the extra money gotten from selling on the market will only benefit the owners but in no way benefit hekdesh (to the exclusion of pesulei hamukdashin where the original redemption price will be determined by how much the meat can be sold for so hekdesh will benefit). By making the heter to sell in the market dependent on whether hekdesh benefits indicates that the issur is only d'rabonon. However, Tosafos in Bechoros proves from or sugya that it must be d'oraysa because the gemara says that since it has these halachos restricting their sale, it is not included in the word בהמתה by an עיר הנדחת because we only include things that can be eaten בתורת בהמתה. If these restrictions would only be d'rabonon, it wouldn't make sense to exclude it from עיר הנדחת based on a pasuk. Tosafos isn't sure what the pasuk would be to forbid this and suggests that there must be some pasuk that forbids degrading hekdesh unless there is a gain for hekdesh. Perhaps the source of this can be the gemara 7a that says that being makdish a ba'al mum is a violation of לא תקריבו even though it only assumes status of kedushas bedek habayis because it is degrading to hekdesh to be makdish a ba'al mum since within the same species there are animals that are fit for a korban - בזיא מילתא וכו' כיון דאיכא במינו. Since the nature of this issur is the degrading of hekesh, perhaps it can be expanded to include the degrading of bechor and ma'aser meat by being sold on the open market.

The Minchas Chinuch (361) cites Tosafos in Zevachim who says that according to some the prohibition is only d'rabonon as the simple reading of the Mishna would imply. If the nature of the prohibition is only d'rabonon, how are we to explain our gemara that exempts it from the שלל עיר הנדחת based on these prohibitions? The gemara darshens from בהמתה to exclude anything that isn't eaten as a regular animal. Although the restrictions against selling and weighing are only Rabbinic, the fact of the matter is that it isn't able to be eaten the way a regular animal is and is therefore excluded from ir ha'nidachas. The Torah may not recognize the Rabbinic issur but nevertheless excludes anything which is practically and actually not treated as a regular animal.

Temurah 4b - When the Torah says not to do it, does it work anyway?

The gemara launches into a major discussion about the concept of כל מילתא דאמר רחמנא לא תעביד, אי עביד לא מהני. Meaning, when the Torah says not to do something, is there a built in mechanism that makes it ineffective even if it is done (rava), or is it effective. The gemara explains that according to Abbaye it must be effective because otherwise there was nothing violated for which to receive malkus, but according to Rava the malkus is for performing the action that the Torah said not to, but it will not be effective.

R. Akiva Eiger (Comments to Y.D. 10:1) explains that the application of this concept is only in cases where by the Torah saying it doesn't work, the Torah is accomplishing something. Meaning, there is a preventative clause built in to any aveira that if the issur can be reduced by it not going into effect, the Torah doesn't enable the issur to go into effect. For example, if one were to shecht on shabbos, the concept of אי עביד לא מהני would not apply to invalidate the shechita because even if the shechita were invalidated, it would in no way reduce the violation of shabbos. We can only apply this concept to a places where by invalidating the effect, it would lessen the violation such as divorcing a woman who one raped. The Torah doesn't want her to be divorced so by invalidating the divorce, the violation is lessened (but the gemara learns from a pasuk that the this is an exception to the rule and the divorce is binding).

Therefore, R. Akiva Eiger asks that if one would shecht an animal with a knife that is forbidden to benefit from because it is avoda zarah, it would make sense to apply אי עביד לא מהני to invalidate the shechita. The benefit from the knive is dependent on the shechita being valid, therefore invalidating the shechita would prevent the violation of benefiting from the knife. R. Akiva Eiger points out based on the Turei Even in Rosh Hashana that even Abbaye who holds אי עביד מהני would only say that in a situation where even if we undermine the effect of the issur, it doesn't negate the fact that he violated the din of the torah. In other words, since even after we undermine the effect of the issur, he nonetheless violated the מימרא דרחמנא (for which rava says he gets malkus), there is no point in negating the effect of his actions since it doesn't truly rectify the violation. However, in a case where undermining the effect will completely undermine the violation, even Abbaye would agree that we apply the concept of אי עביד לא מהני. Therefore, when one shechts with a knife that they are forbidden to derive benefit from, by invalidating the shechita and rendering the animal a ne'veila, we are completely circumventing the violation becasue the violation is not to do an action, it is to benefit. By rendering the animal a neveila it comes out that he never even violated the מימרא דרחמנא so even Abbaye should agree that the animal is considered a ne'veila. R. Akiva Eiger leaves with at צריך עיון.

Erchin 30a - Who can redeem at a prorated rate?

The mishna has various restrictions regarding the rules of redeeming. For example, one cannot sell another property or borrow to obtain capital with which to redeem. Also, one is not allowed to redeem just a piece of the property, they need to wait until they have enough to redeem the entire amount. There is also a system of calculating the redemption price by dividing the sale price by the number of years (with a few more details to compensate for fluctuations in the price of the property, and if it is resold at a different price), from hereon in referred to as prorating. The Rashash questions whether these details of redemption apply specifically to the owner of the property or even to his relatives when they redeem in his place. The Rashash quotes from Toras Kohanim that all the rules apply to the relatives also, except for the concept of prorating which only applies to the actual owner. The Rashash says that the pesukim clearly imply "to one who has a sharp eye" that only for an owner do we prorate to force the buyer to sell him his field back, but when a relative redeems we don't impose this on the original buyer, rather we make the relative redeem at full price.

The Torah talks about prorating both in the context of an inherited field (Parshas Behar 25:25-27) and when one is sold to a ger toshav (48-50). In both places the torah first speaks about relatives redeeming for him but then says that if he comes across money so that he can redeem it by himself or redeem himself, the price is prorated. From this the Rashash understands that it is only prorated when he redeems, not when his relatives redeems.

However, the Meshech Chochma seems to take for granted that even when relatives redeem it is prorated. He asks why does the Torah speak first about relatives redeeming and then about redeeming himself. If relatives can redeem him, surely he can redeem himself when he gets the money together. The Meshech Chochma suggests based on chazal who understand from the pesukim that the prorating must be done meticulously so that the buyer is not being cheated in any way. Therefore, it first says that when relatives redeem we have to be careful to make sure the buyer isn't cheated. Even if the seller himself redeems, he is required to be meticulous about the calculation and not cheat the buyer. The Meshech Chochma seems to understand that both the redemption of the seller and the relatives are included in the system of prorating (unlike the rashash) but it is more of a chiddush to say that even the seller himself must be meticulous about the calculation.