1) HALACHAH: THE CAT KILLED BY MICE
QUESTION: The Gemara discusses an incident in which a person borrowed his friend's cat (to catch mice), and the mice ganged up on the cat and killed it. (This is the case according to the first version as cited by the Gemara. According to the second version, the cat ate too many mice and became ill as a result and died.) Rav Ashi questioned whether such a case is considered "Meisah Machmas Melachah" for which a Sho'el is exempt. TOSFOS (DH Ki Hai) explains that Rav Ashi reasoned that it might not be considered a case of "Meisah Machmas Melachah" because the Sho'el brought the cat to a place that was infested with mice. By bringing it to a place with so many mice, he may have placed the cat in a situation to which it was not accustomed, and therefore he would be Chayav for the cat's death. Rav Mordechai suggested to Rav Ashi that the case is comparable to a case of a man who was killed by women, in which case the man should not have been overpowered by them. Similarly, the cat should not have been killed by the mice, and thus the Sho'el should be exempt from liability. This is the way the REMA (CM 340:3) rules.
The TERUMAS HA'DESHEN (#328) cites this Gemara as proof for a ruling he issued in response to a certain question that was asked of him. An armed group of robbers had besieged a town and planned to plunder and steal all of the animals of the town. The townspeople armed themselves and prepared to go to battle with the robbers to save their flocks. Reuven borrowed from Shimon a coat of armor and weapons so that he could join the legion going to fight the robbers. However, those who went to battle were defeated, and the robbers stripped them and took all of their belongings, including their weapons. The borrowed armor and weapons were also taken away. Is Reuven obligated to pay Shimon for the loss of the armor and weapons? This was the question posed to the Terumas ha'Deshen.
ANSWER: The Terumas ha'Deshen ruled that Reuven was not obligated to pay. Even though a Sho'el is obligated to pay in the event of loss due to an Ones, in this case the Sho'el was exempt because the loss of the armor and weapons was considered "Meisah Machmas Melachah." Even though the weapons did not actually break in the course of normal usage (which is the common definition of "Meisah Machmas Melachah"), nevertheless since they were lost due to the very Melachah for which Reuven borrowed them, it is considered a case of "Meisah Machmas Melachah" and he is exempt.
The Terumas ha'Deshen cites proof for his ruling from the case of the cat that was killed by mice. The Gemara debates whether it was a case of "Meisah Machmas Melachah" or whether the Sho'el acted negligently when he brought the cat to a place teeming with mice. It is clear, however, that if the Sho'el had used the cat in a normal manner, such as in a house that had only a few mice, he would not have been obligated to pay for the demise of the cat even if the same Ones had occurred. Even if the mice had attacked and killed the cat while it was not involved in chasing and catching them (which is the Melachah for which he borrowed the cat), it would have been a clear case of "Meisah Machmas Melachah." (The Terumas ha'Deshen understands, according to the Gemara's first version of the case, that the mice's killing of the cat had no connection with the Sho'el's intent to use the cat to catch the mice. According to the second version of the case, in which the cat caught and ate too many mice and died as a result, the BACH (CM 340, in explanation of the Ramah cited by the Tur there; see also S'MA there) explains that in that case, too, the death of the cat was not related to the Melachah for which he borrowed the cat. He borrowed the cat in order to catch and kill the mice, and not to eat them. The Terumas ha'Deshen, however, explains that his proof is only from the first version, in which the cat's death was not related to its Melachah of catching mice.) The Terumas ha'Deshen asserts that although the borrowed armor and weapons were not lost as a result of the Melachah for which they were borrowed, nevertheless their loss is considered "Meisah Machmas Melachah," because the loss occurred as a result of the usage for which he borrowed them.
The SHACH (CM 340:6), however, says that there is an important difference between the case of the borrowed cat and the case of the borrowed weapons. He maintains that only the borrowed cat that was killed by mice can be considered "Meisah Machmas Melachah," since the mice killed the cat as a result of the Melachah that the cat wanted to do on its own accord (i.e. to chase and kill mice). The lender was at fault because he lent a cat that would be unable to withstand an onslaught of mice. In contrast, in the case of the borrowed weapons, the weapons themselves certainly did not do any Melachah on their own accord. Rather, the Sho'el used them for battle. As a result of his failure to prevail in combat, the weapons were captured, and the lender is not to blame (for there was nothing wrong with the weapons that he lent to the borrower). Hence, the confiscation of the weapons is considered an Ones, and not "Meisah Machmas Melachah," and thus the Sho'el is Chayav.
2) HALACHAH: LIGHT WORK WITH "BA'ALAV IMO"
QUESTION: Rava says that if one wants to borrow something and be exempt from all liability, he should ask the lender, at the time that he borrows the item, to give him a drink of water. The lender thus performs work for the Sho'el and the case is one of "Ba'alav Imo," in which case the Sho'el is exempt from liability.
The Gemara has discussed the concept of "Ba'alav Imo" at length, and it has established that when the owner of the item performs work for the Sho'el, the Sho'el is exempt from liability. What is Rava adding that was not already known?
ANSWER: The RITVA (Yeshanim) answers that Rava is teaching that even when the owner performs merely a small, light task, he is considered "loaned" to the Sho'el for this Melachah and the She'eilah is considered "She'eilah b'Ba'alim" to exempt the Sho'el. (I. Alsheich)