Shiur Supplement #21 Daf 21b
A. Amar Chizkya [lines 14-19] Chizkiya concludes that it is forbidden to BENEFIT (hana'a) from chametz on Pesach based on the verse (Shemot 13:3): "Lo yei'akhel chametz" (chametz shall not be eaten). This implies that not only is the PHYSICAL action of eating prohibited but, in fact, any activity with chametz that could LEAD to the act of eating even non-chametz food, is also forbidden. Thus, one may not benefit from the chametz, for example by selling it, as the money could be used to buy food. Once the general prohibition against gaining hana'a is derived, it applies across the board, even in a specific instance that the resultant benefit will not lead to eating. By using the term "lo yei'akhel," the Torah prohibits the general type of activity that leads to aquiring food. However, the term "lo yokhal" implies only that it is forbidden to EAT - gaining hana'a IS allowed.
B. U-plga de-Rabbi Abahu [lines 19-35] According to R. Abahu, the Torah forbids hana'a even by the usage of the term "lo yokhal etc." unless stated explicitly that it is permitted to benefit. He proves this using the case of neveila (an animal which was killed NOT by slaughtering and is forbidden to be eaten). Although the Torah uses the terminology of "lo tokhlu" it states explicitly that one MAY benefit from the meat of a neveila. From this we can deduce that had the Torah not granted express permission, it would be forbidden to benefit, in any way, from the chametz.
R. Me'ir and R. Yehuda as to how exactly one may dispose of the neveila by giving or selling it to others.
C. Mi-lakelev tashlichun oto [last line] R. Abahu claims, that according to R. Yehuda, we learn the rule that issur hana'a is implied in the term "lo yokhal etc." from the law of tereifa (an animal that was slaughtered correctly but may not be eaten as it has a defect that would have lead to its pre-mature death). The Torah states that the meat of this carcass may be fed to the dogs. From this we deduce that only in the case of tereifa may one benefit from the meat (by feeding it to the dogs). In other cases, however, it is forbidden to benefit in any way.