Reuven borrowed a bucket from Shimon, and it broke.

Rav Papa: Bring witnesses that you did not use it abnormally, and you are exempt.

Version #1: Reuven borrowed a cat from Shimon, and mice ganged up on it and killed it.

Question (Rav Ashi): Is this like dying during work?

Answer (Rav Mordechai): Yes. (He was not negligent for putting it in a dangerous place. A proper cat would not be killed by mice.)

Version #2: Reuven borrowed a cat from Shimon, and it ate too many mice, got overheated and died.

Question (Rav Ashi): Is this like dying during work?

Answer (Rav Mordechai): Yes. (He was not negligent; the cat killed itself.)

(Rava): If one wants to borrow something and be exempt, he should ask the lender 'give me a drink of water.' This is b'Ba'alim.

If the lender is sharp, he will tell the borrower 'I will give you after you take the object.'

(Rava): If any of the following lends (to the one he works for) while working, it is considered b'Ba'alim: a teacher of children (who lends to the parents), one hired to plant a vineyard for half the Peros, a slaughterer, a blood-letter, and the town Sofer (scribe, or barber).

Rabanan (to Rava): You work for us (you teach us. If we borrow from you, we are exempt.)

Rava: No, you work for me. I decide which tractate we learn, and you cannot protest!

The Halachah is, in the period before the festival, when the Rebbi must teach laws of the festival, he works for them. At other times, they work for him.

Mereimar bar Chanina rented a mule to people of Bei Chuzai. He went out to help them load it. They were negligent, and it died; Rava obligated them to pay.

Rabanan: This is negligence b'Ba'alim!

Rava was embarrassed. Later, it was found that Mereimar did not go to help, rather to ensure that they did not overload his mule.

Question: Granted, according to the opinion that exempts negligence b'Ba'alim, we understand why Rava was embarrassed;

According to the opinion that obligates negligence b'Ba'alim, why was he embarrassed?

Answer: It was not a case of negligence. Rather, it was stolen and died in the thief's premises. Rava obligated them to pay.

Rabanan: This was b'Ba'alim!

Rava was embarrassed. Later, it was found that Mereimar did not go to help, rather to ensure that they did not overload his mule

(Mishnah): Reuven borrowed Shimon's cow for half the day and rented it for half the day, or he borrowed it for today and rented it for tomorrow, or he borrowed one cow and rented another; the cow (in the last case, one of them) died.

If Shimon claims that the borrowed cow died (or, in the first cases, that at the time it died it was borrowed), and Reuven is unsure, he must pay.

If Reuven claims that the cow that died was rented, and Shimon is unsure, Reuven is exempt.

If Shimon claims that the cow that died was borrowed, and Reuven says that it was rented, Reuven swears that it was rented and he is exempt.

If both are unsure, Reuven pays half.

(Gemara) Inference: If Levi claims that Yehudah owes him money and Yehudah says 'I don't know', he must pay.

Suggestion: This refutes Rav Nachman!

(Rav Huna and Rav Yehudah): If Levi claims that Yehudah owes him money and Yehudah says 'I don't know', he must pay;

(Rav Nachman and R. Yochanan): Yehudah is exempt.

Rejection: No. Our Mishnah discusses a case like Rav Nachman said (elsewhere), that Reuven must swear to Shimon (about something else. Therefore, Shimon can demand that he include in the oath that the borrowed cow did not die. Reuven must swear, and he cannot, for he is unsure, so he must pay.)

Question: In what case must Reuven (pay because he cannot) swear to Shimon?

Answer: It is a case like Rava taught;

(Rava): If David claimed 100 from Moshe, and Moshe admits to 50, and he does not know about the other 50, since Moshe must swear and he cannot, he must pay.