Yevamos 36a - 1. Oleh l'yibum o'leh l'chalitza. 2. Chalitzah after Bi'ah to Meuberes

2 points:

1. R' Elchonon (38:3) points out that normally the rule of kol ha'ola l'yibum.... means that if there is zikas yibum then there is chalitza, to the exclusion of a case where there is no zikas yibum. But here, the gemara can't possibly mean that rule, since there is zikas yibum even when she is pregnant (bec. even acc. to reish lakish there is no issur eishes ach to have biah with her when she is pregnant so long as the vlad turn out to be not shel kayama as we said yesterday - the reason why there is no issur eishes ach is bec. there is zikah). Rather, the gemara means that in a situation where yibum cannot be performed now bec. the bi'ah will not be effective to be koneh her and patur the tzarah, the chalitza will also not be effective. This is very meduyak in rashi on the top of the page vs. rashi 44a.

2. Yesterday I pointed out that acc. to reish lakish, rashi explains that the bi'ah while she is pregnant (in a case where she later miscarries), aside from not being an issur eishes ach, makes it impossible to free her with chalitzah. Rashi is medayek this from the mishna and gemara which says that the only solution is to do yibum after she miscarries, which implies that there is no other solution. However, the maharsha 36b explains that rashi 36b when he says that she needs a get but does not need chalitzah is going acc. to r' yochanan, but acc. to reish lakish he would need a get and chalitzah (see also tosfos yeshanim). From the maharsha we see that even after he had bi'ah there is a solution to free her by a get and chaltizah, the chalitzah would be deoraysa and the get would be derabonon as a penalty for entering a safek. This seems to contradict rashi 35b who understands that once bi'ah was done, chalitzah no longer works mideoraysa?