Siman - Pesachim Daf 21

• כל שעה שמותר לאכול מאכיל

The opening Mishnah of the second perek states, שעה שמותר לאכול מאכיל לבהמה לחיה ולעופות –  - As long as it is permitted to eat chametz, one may feed chametz to domesticated animals, beasts and birds. The Gemara infers from here that as long as it is not permitted to eat chametz, meaning, once the prohibition begins, one may not feed it to animals, and determines that this ruling does not fit with Rebbe Yehudah or Rebbe Meir from the Mishnah on 11b regarding when chametz becomes prohibited.

Rabbah bar Ulla said the Mishnah is in accordance with Rabban Gamliel who held that chametz that is chullin may be eaten the entire fourth hour, terumah that is chametz may be eaten by a Kohen the entire fifth hour, and the chametz must be burned at the beginning of the sixth. Our Mishnah is saying that as long as a Kohen may eat chametz that is terumah during the fifth hour a non-Kohen may feed chametz that is chullin to the animals, but he may not eat it.

• Why mention beheimos, chayos and ophos?

The Gemara asks why the Mishnah listed three categories of animals and explains:

If the Mishnah only listed beheimos one might have thought that it only applies to them because if they leave over any chametz one can see it and then get rid of it. Rashi explains that they do not hide their food. Chayos hide their food and therefore if one were to feed them, he might not be able to find the chametz in time to get rid of it.

If the Mishnah only listed chayos one might have thought that since they hide their food, at least if they leave some over, they will hide it. If the owner cannot find it, he will only transgress בל ימצא - not to find. If a beheimah leaves over food, however, the owner might not have in mind to be mevatel it and then he will transgress both בל יראה ובל ימצא – not to see it or find it.

Once the Tanna mentioned beheimos and chayos, he also mentioned birds.

• The source for not getting הנאה from chametz

The Gemara brings a machlokes regarding the source for the prohibition against deriving benefit from chametz.

Chizkiyah derives it from the passuk, לא יאכל חמץ – chametz shall not be eaten, which is understood to mean, לא יהא בא היתר אכילה – there shall not be associated with chametz any permissibility that leads to eating. Rashi explains that any monetary gain will bring one to purchase food.  Rebbe Abahu stated, כל מקום שנאמר "לא יאכל", "לא תאכל", "לא תאכלו" – anywhere where the passuk reads, one shall not eat, or you (singular) shall not eat, or you (plural) shall not eat, אחד איסור אכילה ואחד איסור הנאה משמע – both a prohibition against eating and deriving benefit are inferred, unless the Torah specifies otherwise as it does regarding neveilah.