1) A "BOR" WHICH DAMAGES FOOD ITEMS
QUESTION: The Gemara says that the owner of a Bor is obligated for damages caused to items that are covered ("Nizkei Tamun"). RASHI (DH Shiyer) explains that this refers to a case in which a donkey falls into a Bor while carrying a sack full of grain. If the grain becomes ruined, the owner of the Bor is obligated to pay for it even though it was inside of a sack.
It seems from the words of Rashi that, normally, the owner of a Bor is obligated for damage done to food by his Bor. Although the Gemara (28b) derives from the verse that one is obligated for "'Chamor' (Shemos 21:33) v'Lo Kelim" -- one is not obligated to pay for damage done to Kelim that fall into his Bor -- this does not apply to food items, but only to Kelim.
TOSFOS (DH Shiyer) asks that the Gemara later (48b) implies that food is in the same category as Kelim, and the owner of a Bor is exempt from damage done to food. The Gemara there says that if a Bor spoils a person's water, the owner of the Bor is exempt because "water is like Kelim" (see also Rashi there, DH u'Mayim Kelim). The Gemara must be referring to an animal that is inside of a sack that falls into a Bor, as Rashi explains later (26a, DH she'Ken Yeshno b'Bor). How will Rashi explain that Gemara?
ANSWERS:
(a) According to the MESHECH CHOCHMAH cited earlier (see Insights to 4b), Rashi exempts the owner of a Bor that is ten or more Tefachim deep from damages done to a person (Nizkei Adam), because a person is not expected to fall into a Bor since he avoids potentially fatal obstacles. The owner of the Bor did not have to protect it from people falling into it. The Meshech Chochmah adds that the same logic might apply to the reason why the Torah exempts a Bor from Nizkei Kelim, damages done to Kelim. A person does not normally load his Kelim upon a donkey, lest the donkey stumble and the Kelim fall and break.
If this logic is correct, perhaps the Torah only exempts a person from damage caused to fragile or breakable Kelim, because people do not load them onto animals lest they break. However, people do load food upon animals, since food is not likely to become ruined if the animal stumbles. Even if the sack containing the food tears, the food itself can be washed and used. However, this applies only to solid food. Liquid food -- which requires a container when transported -- will become lost entirely if its container breaks, and therefore it is not usually loaded upon an animal. That is why the Gemara later (48b) writes with regard to damage caused by a Bor to water that it has the same Halachah as damaged caused by a Bor to Kelim. (M. Kornfeld)
(b) RASHI (3a) writes that the verse in the Torah discusses only a Bor that is ten Tefachim deep. As explained earlier (see Insights to 4b), the verse excludes damages caused to a person by a Bor only when the Bor is ten Tefachim deep. However, one is exempt for damages caused by his Bor to Kelim even if the Bor is less than ten Tefachim deep (see Gemara 53b). How can such damages be excluded from the verse, which is discussing a Bor that is ten Tefachim deep?
Perhaps there is a different reason for why a nine-Tefach Bor is exempt from Nizkei Kelim. It is exempt not because of the Mi'ut of the verse in the Torah ("'Chamor' v'Lo Kelim") but because a nine-Tefach Bor is liable only for causing damages and not for causing death. Any damage that happens to a Kli is not considered damage but is considered Misah, the "death" of the Kli (see RASHI to 28b, DH v'Chelim Peturin).
Hence, there might be a difference between a ten-Tefach Bor and a nine-Tefach Bor with regard to damage done to food. The Torah excludes a ten-Tefach Bor only from damage done to Kelim ("'Chamor' v'Lo Kelim"). That is why Rashi here, who is discussing a ten-Tefach Bor like the Bor of the Mishnah, writes that the owner of the Bor is liable for damages done to Tevu'ah (produce). However, a nine-Tefach Bor, which can cause only damage and not death, incurs no liability for damage done to Kelim or to food, since any damage done to such items is considered to be the "death" of the item. That is why the Gemara (48b) states that the owner of a Bor is exempt for damage caused to water; it is discussing a Bor that cannot cause death (i.e. a nine-Tefach Bor).

10b----------------------------------------10b

2) A HEAVY PERSON WHO BREAKS A BENCH
QUESTION: The Beraisa teaches that if five people sat on a bench and it did not break, and then one person came and sat on it and it broke, the last person is liable to pay for the damages. Rav Papa says that this refers to a person "like Papa ben Aba." Rashi says that Papa ben Aba was heavy.
What is the significance of the fact that the person who broke the bench was heavy? Would the Halachah differ if the person was not heavy?
ANSWERS:
(a) TOSFOS (DH Kegon) in the name of the RASHBAM explains that when a person is invited into the home of another, the invitation includes permission to sit on any of the seats or benches in the house, but only if the person is not extremely overweight. If the person is extremely overweight, the invitation does not include permission to sit on the benches in the house. Therefore, if the person who broke the bench was not very heavy, he would not be obligated to pay for the damages since he was permitted to sit down on them. He is considered a "Sho'el" (borrower) who is exempt from paying for an item that breaks in its normal course of usage ("Meisah Machmas Melachah"). A person like Papa bar Aba, however, would not have permission to sit on the bench, and thus he would be liable for damaging it.
The Rishonim ask a number of questions on this approach.
According to the Rashbam, even if the heavy person was not the last person to sit on the bench but was the first person to sit down, he should be liable if the bench breaks since the others (who are of normal weight) used the bench with permission, while he used it without permission. (RABEINU YESHAYAH cited by the Shitah Mekubetzes)
Moreover, when the Gemara suggests that the bench eventually would have broken without the last person sitting on it but since he sat there it broke sooner, the Gemara finds it necessary to explain why the other people sitting on the bench are exempt. The Gemara says that they could claim, "Had you not sat down, we would have been able to sit longer, and therefore we should not be liable." The Gemara rejects this claim by asserting that they should have arisen immediately when they saw the heavy person sit down next to them on the bench.
Why, though, do the others need any excuse to exempt themselves? The reason they are exempt is because they sat there with permission because they are of normal weight! (Ibid.)
RABEINU YESHAYAH answers that one question answers the other. The fact that the Beraisa obligates the heavy person only because he is the last one who sat there implies that the other people who sat on the bench are also overweight. That is why the last person to sit down is liable only if he is the last one to sit there. Otherwise, he would be exempt and the heavy person who did sit there last would be obligated instead, since he sat there without permission. (Although the other heavy people also sat there without permission, "the bench would not have broken if he (the last one) had not sat there.")
This answers the second question. The Gemara needs to find an excuse to exempt the first people who sat on the bench because they, too, were heavy (and sat there without permission), which is clear from the fact that the person who broke the bench is liable only because he was last. (See TALMID RABEINU PERETZ cited by the Shitah Mekubetzes who offers a different answer to these two questions.)
(b) TOSFOS cites RABEINU TAM who answers that Rav Papa explains that the person who broke the bench was heavy because the Gemara concludes that that person is liable since he leaned on the people who were sitting on the bench. He put his weight on the bench and, at the same time, prevented the others from standing up. If he was not very heavy, he would not have been able to prevent the others from standing up.
According to this approach, Rav Papa actually answers his own question. Rav Papa asked why the Gemara does not explain that the Mishnah's case is the same as the case of the Beraisa, in which the last person broke the bench? Rav Papa himself immediately answers that in the Beraisa's case the last person pushes down on the bench and on the people on it, thereby causing all of the damage and not just the final blow. (According to Rabeinu Tam, the proper Girsa is "Amar Rav Papa" and not "v'Amar Rav Papa" as it appears in our texts.) The Gemara then articulates why Rav Papa finds it necessary to explain the Beraisa in this way. (RASHBA)
According to Rabeinu Tam, it cannot be proven from this Gemara that a person is permitted to sit on a bench in any house into which he is invited.
(c) The ME'IRI writes that Rav Papa made his comment in a light-hearted manner. He was commenting that it must have been a very heavy person who broke the bench. (Rav Papa himself was known to be heavy (Bava Metzia 84a), and perhaps he was giving himself as an example when he said this, saying that he would have broken the bench had he sat there.)