1) TWO COWS
QUESTION: The Mishnah (97b) teaches that when the lender claims that the cow that he lent to the borrower is the one that died (and thus the Sho'el is Chayav), and the borrower says that he is unsure which one was the cow that died, the borrower must pay. The Gemara explains that the Mishnah refers to a case in which the borrower is already obligated to make a Shevu'ah about something else, and the lender therefore may demand that the borrower include in the Shevu'ah that he is not liable for the cow. The borrower must pay because he is obligated to swear but is unable to swear (since he is unsure).
The Gemara says that the first two cases of the Mishnah must involve two cows, and the last case must involve three cows, in order for the Mishnah to be understood as a case in which there is an additional obligation of a Shevu'ah. In the first two cases, Reuven must have borrowed from Shimon two cows for half the day and rented them for half the day (or borrowed them for one day and rented them for the next), and both cows died. Shimon claims that both died at the time they were borrowed, and Reuven admits that one died when it was borrowed, but he is unsure about the other. Since Reuven is obligated to swear but cannot swear, he must pay.
RASHI (DH Ka) explains why the Gemara needs to say that both of the cows died. In a case in which only one of the cows died and Shimon demands both cows from the borrower, when Reuven returns the cow that did not die he would not have to make a Shevu'ah on the other cow. When he returns the live cow, it is considered "Heilach," and, according to one opinion (4a), a case of "Heilach" is not considered "Modeh b'Miktzas" and the borrower does not have to make a Shevu'ah. Therefore, it must be that both cows died, and the borrower admits to one ("Modeh b'Miktzas") and is unsure about the other.
Why, though, must the Gemara say that both cows died? It could have said that only one cow died, and when Shimon demands his two cows from Reuven, Reuven admits that he must return one live cow but says that it is in the marsh (and he is not returning it at that moment), and he says that he is unsure whether the one that died was borrowed or rented when it died. In such a case the borrower should be obligated to make a Shevu'ah of "Modeh b'Miktzas," since he does not say "Heilach." Why does the Gemara not explain the case in this manner?
(a) The BA'AL HA'ME'OR (cited by the Shitah Mekubetzes), the RASHBA, and the ROSH maintain that, in fact, it is considered a case of "Heilach" whenever a borrower admits to part of a lender's claim but does not return it at that moment and instead says that the object is located somewhere else. They prove this from the fact that the Gemara does not explain the case here in this manner; since the Gemara does not give this explanation, such a case indeed must be considered "Heilach." In fact, Rashi himself (4a) maintains that it is considered "Heilach" as long as the original object is still present even though it has not yet been returned.
(b) The RA'AVAD (98b) argues with the Ba'al ha'Me'or's assertion and maintains that the only case of "Heilach" is a case in which the borrower immediately returns part of the lender's claim. If the borrower admits to part of the claim and says that the item is elsewhere, it is not a case of "Heilach."
The Ra'avad therefore gives a different answer to the above question. The Ra'avad says that when a person claims that he is owed a borrowed item (She'eilah) and a rented item (Sechirus), he is considered to have made two separate claims. Therefore, when Reuven admits that he must return one borrowed cow to Shimon, but he says that the other cow might have been rented when it died, he is responding to two separate claims and not to a single claim. Hence, he is not considered "Modeh b'Miktzas" to one claim involving two cows, but rather he has admitted to a separate claim in itself.
Based on this, the Ra'avad rules that in a case in which a claimant says, "I lent you 100 Zuz, and I deposited with you 100 Zuz for safekeeping," and the defendant denies having borrowed any money but admits that 100 Zuz were given to him as a deposit, this is not considered "Modeh b'Miktzas" and the defendant does not make a Shevu'ah of "Modeh b'Miktzas."
The RAMBAN, however, argues with the Ra'avad and maintains that a claim that includes She'eilah and Sechirus is considered a single claim and not two separate claims. In the Gemara's case, therefore, the borrower's claim is considered "Modeh b'Miktzas." The Ramban also argues with the Ra'avad's comparison of this case to a case of a person who denies that he borrowed money but admits that he received money as a deposit. Even if a claim involving both She'eilah and Sechirus would be considered two separate claims, a claim of money loaned and a claim of money deposited would be considered one claim and thus a Shevu'ah of "Modeh b'Miktzas" would apply (because the claim is that the defendant owes money; it does not matter why he owes the money).
2) SEND THE COW WITH MY SON
QUESTION: The Mishnah teaches that when a Sho'el borrows a cow and tells the owner, "Send the cow with my son or with my servant," the Sho'el becomes responsible for any Ones that occurs to the cow while it is being brought to him.
Why, though, should he be Chayav? The Sho'el did not speak to the person bringing the cow and he did not formally appoint him as his Shali'ach. (RA'AVAD and RAN cited by the Shitah Mekubetzes)
(a) The RA'AVAD cited by the Shitah Mekubetzes answers that when the Sho'el told the owner to send the cow with his son or servant, he was appointing the owner as his Shali'ach to appoint the messenger as a Shali'ach to bring the cow.
(b) The RAN cited by the Shitah Mekubetzes explains that the Sho'el becomes Chayav for Onsin because of the law of "Arev." When an Arev guarantees a loan, the Arev becomes obligated to repay the loan (if the borrower cannot) because the lender gave money to the borrower only as a result of the Arev's promise that he would back the loan. Similarly, in the Mishnah's case, the owner gave the cow to the Sho'el's son or servant only because of his reliance on the Sho'el's word that he would be responsible for Onsin. (See also Insights to Bava Metzia 73:1 and 76:1.)
The NESIVOS HA'MISHPAT (CM 340:11, as cited by the YOSEF DA'AS) points out that there are important Halachic differences between these two answers. According to the Ra'avad who says that the Sho'el is obligated for Onsin because the messenger becomes his Shali'ach, if the Sho'el requested that the cow be sent to him in the hands of a Cheresh, Shoteh, or Katan, he would not be Chayav for Onsin because none of those people can be appointed as a Shali'ach. According to the Ran, who says that the Sho'el is Chayav for Onsin because he is like an Arev, even if the person who brings the cow to him cannot be a valid Shali'ach, the Sho'el still would be Chayav because of the Halachah of Arev.
Another difference between the two answers relates to whether the owner may change his mind and take back the cow. According to the Ra'avad, once the cow is placed in the hands of the Shali'ach, the owner cannot take it back since it is considered to have come into the domain of the Sho'el. According to the Ran, he may take it back since it was not given to a Shali'ach of the Sho'el and thus is not yet considered to have come into the Sho'el's domain.