Explanation: It was exhausted due to Melachah.

Even though it died due to Melachah [for which a borrower is exempt], in any case, since he deviated, he is liable;

If he was supposed to take it in the mountain, it is possible that had he taken it there, it would not have become weary, due to the air and wind there;

Or, if he was supposed to take it in the valley, [perhaps] it would not have become weary, for there is not the exertion [of ascent] like there is in the mountain.

Therefore, he is liable even according to the opinion that exempts when the beginning was negligence and the end was Ones.

Question (Rivam): Rabah said that the case is, a snake bit it. According to him, why did [the Mishnah] discuss a mountain and a valley?

It could have discussed a valley and a valley, if it is known that snakes are found today in the valley that he deviated to take it there;

This mishap does not change between a mountain and a valley more than between a valley and another valley!

Answer (Ri): Rabah answered l'Tamei (according to his opinion). He holds that if the beginning was negligence and the end was Ones, he is liable;

It connotes like this below (93b), for Abaye asked him "why is he exempt? The beginning was negligence and the end was Ones!" (If Rabah holds that one is exempt in such a case, this is not difficult at all!)

Support: This is why it mentioned a mountain and a valley, for now the beginning was negligence regarding overheating or slipping;

However, if he changed from a valley to another valley, he is exempt, for the beginning was not negligence.

Citation (Bava Kama 56a - Rabah): The case is, the animal tunneled [under the wall and left through the opening];

Citation (cont.) Question: This is fine for the opinion that exempts when he was negligent at the beginning and Ones at the end. However, according to the opinion that obligates, how can we answer?

Observation: If the text here and there is "Rabah", we could have asked a contradiction in Rabah, for here he holds that he is liable.

Explanation: All the Amora'im who come to answer here [why he is liable in the Reisha] hold like Rava, who says [when it died normally] that the angel of death would have killed it no matter where it was;

According to Abaye, who says that the air of the swamp killed it, our Mishnah is fine without these answers. He is liable even if it died normally.

He says that the air to which he brought it killed it, even if it is not known that that air is any worse than other air;

He did not say specifically "the hot air of the swamp." The same applies to any change of air, like is proven in the Sugya there.

Implied question: Why does the Seifa say that if it slipped on the mountain or overheated in the valley, he is liable? The same applies if it died normally, since the beginning was negligence!

Answer: It is because in the mountain he is exempt. It taught about overheating to teach that even though heat is a reason to be exempt in the mountain, in the valley he is not exempt for this. Just the contrary, it is a reason to be liable!

Question: We learn this from the Reisha! Even if it died normally, he is liable because the beginning was negligence regarding slipping on the mountain, and heat in the valley;

All the more so he is liable when it died through slipping on the mountain or overheating in the valley!

Answer: Had the Seifa not taught this, we would not know why the Reisha is considered that the beginning was negligence, to obligate him even if it died normally.

Question: According to Rava and all the Amora'im here who exempt when it died normally, why did the Seifa teach that he is exempt for overheating in the mountain and slipping in the valley?

It should have taught a bigger Chidush, that if it died normally he is exempt, for we do not say that the air of that place killed it!

All the more so [he is exempt for] overheating in the mountain and slipping in the valley, for surely, had he not changed, it would have died in this way.

Answer #1: Because it taught slipping due to liability in the mountain, it taught [slipping] also regarding exemption in the valley.

Answer #2: The exemption for overheating in the mountain and slipping in the valley is a bigger Chidush than when it died normally;

A person can be more careful about these (overheating and slipping) than dying normally. We should say that he was negligent for changing;

Had he taken it in the mountain, he would have been very meticulous and guarded it well lest it slip in the mountain or overheat in the valley. However, his change caused that he was not meticulous.

Question: It is difficult that Abaye argues with all of the Amora'im!

It is not considered negligence to change, because he can be careful and very meticulous that it not slip in the mountain or overheat in the valley;

Abaye agrees that he is exempt if it died normally, since the beginning was not negligence.

Observation: Rabah, who says that the case is, a snake bit it, he must say that sometimes snakes are more common in the mountain than in the valley, or oppositely. Therefore, it mentioned a mountain and valley.

It is fine for Rabah that even if the beginning was negligence and the end was Ones, he is exempt.