1) THE LIABILITY OF A POTENTIAL BUYER WHO EXAMINES AN OBJECT FOR SALE
QUESTION: The Gemara discusses the liability of a buyer who makes a conditional purchase on a gift for his Kalah ("Arusaso"). The Gemara describes a case in which the buyer takes an object from a craftsman to send to his Kalah and stipulates that if she does not want the object, he will return it and pay a minimal sum for having taken the object on a trial basis. If the object is damaged or destroyed through an Ones on the way to the Kalah, the buyer is fully responsible to pay for it. If the Ones occurs during the return trip, however, he is exempt, because during the return trip he is only a Shomer Sachar (who is exempt from liability in cases of Onsin).
In two other places, the Gemara seems to give contradictory explanations as to why a potential buyer is liable for Onsin when he takes an object to check if he wants to keep it.
The Gemara in Nedarim (31a) understands that his liability is because he has the status of a Sho'el. The Gemara there says that he has the liability of a Sho'el because he, the potential buyer, is the sole beneficiary of the usage of the object ("Kol Hana'ah Shelo"). The Gemara posits that this Halachah makes a buyer liable only when he purchases an object that is in high demand and is easily sold, in which case the seller does not benefit from the fact that the buyer considers purchasing the object, because he can easily find another buyer. An ordinary Sho'el's liability also results from the fact that he is the sole beneficiary, and thus the potential buyer is comparable to a Sho'el.
However, the Gemara in Bava Basra (88a) gives an altogether different explanation for the potential buyer's liability. The Gemara there says that one who takes an object to examine it before buying it is liable for an Ones only when the object's price has been fixed. This implies that the liability for Onsin in a conditional purchase is a function of the person's status as a buyer. The fixed price causes him to be considered a buyer, because when he takes the object to examine it his actions indicate that he is definitely interested in buying it and is not concerned by the price; he merely wants to examine it to see if it is in good condition. The element of a fixed price, however, plays a role only in a sale, where one is interested in buying the object, but as far as a Sho'el is concerned the presence of a fixed price is totally irrelevant. The Gemara in Bava Basra cannot be understood to mean that a potential buyer becomes like a Sho'el, because the presence of a fixed price would not affect his status in that respect. Thus, the Gemara in Nedarim and the Gemara in Bava Basra seem to contradict each other as to whether the liability for Onsin is that of a buyer or that of a Sho'el.
ANSWER: The SHITAH MEKUBETZES here reconciles the two Gemaras and explains that both Halachos are correct. When a person takes an object with a fixed price to examine it, he is considered a buyer, in which case he is liable even if the object is not easily sold (and is not "Kol Hana'ah Shelo"). If, on the other hand, no price has been fixed, he cannot be considered a buyer, but he might still be liable for Onsin as a Sho'el if the object can be sold easily and the sale is considered a favor for the buyer. In such a case, when the buyer takes the object to examine it, he is the only one who benefits ("Kol Hana'ah Shelo") and he is deemed a Sho'el and therefore is liable for Onsin. (See NESIVOS HA'MISHPAT 186:1 for further discussion of the answer of the Shitah Mekubetzes.) (Y. MARCUS)
2) DOES THE LOAN OF AN OBJECT CONSTITUTE "BA'ALAV IMO"
OPINIONS: The Gemara says that if two people give each other an object to guard on the same day, each Shomer is exempt from liability for Onsin because of the Halachah of "Ba'alav Imo," which states that when a Shomer watches an object while the owner is "with him" (i.e. working for him), the Shomer is exempt (see Shemos 22:13-14). The Gemara explicitly says that when two people act as Shomrim for each other, this constitutes "Ba'alav Imo." What is the Halachah when two people borrow objects from each other? Does that also constitute "Ba'alav Imo"?
(a) RASHI (DH Shemirah b'Ba'alim) maintains that when one person (Reuven) borrows an object from another person (Shimon), and then Reuven, the borrower, himself lends a different object to Shimon, the lender is not considered "Ba'alav Imo." That is, Reuven is not considered to be doing work with Shimon such that Shimon would be exempt from Onsin. Rather, they each have the full liability of a Sho'el.
(b) The RAMBAM (Hilchos Sechirus 10:2) maintains that when Reuven borrows an object from Shimon, and then Reuven himself lends a different object to Shimon, Reuven is considered "Ba'alav Imo."
The S'MA (CM 305:8) explains that the Rambam maintains that since a person who borrows an object is obligated to guard the object, he is considered to be working for the lender and is thus "Ba'alav Imo."
The NESIVOS HA'MISHPAT (305:2) writes that Rashi disagrees because he maintains that since a Sho'el is the sole beneficiary when he borrows an object ("Kol Hana'ah Shelo"), even his obligation to guard the object is considered to be for his own benefit. According to this explanation, Rashi might consider even a Socher to be "Ba'alav Imo" to the owner of the object, because he is guarding the object for his own benefit (that is, he must keep it guarded in order to use it).
RAV ELCHANAN WASSERMAN Hy'd in KOVETZ SHI'URIM (Kesuvos 34b, DH Hani'ach Avihen) offers a different explanation for the opinion of Rashi. Since a Sho'el is obligated even for an Ones, the object is considered to be in his possession temporarily. Consequently, he has no obligation to the object's owner to guard it, but rather he must guard it for his own benefit, in order to be able to return it after the termination of the period of She'eilah. According to this explanation, in the case of a Socher -- who is not liable for Onsin -- the Socher's obligation to guard the object certainly would be for the benefit of the owner, and he would thus have the status of "Ba'alav Imo" to the owner, even according to Rashi.
(The opinions of both Rashi and the Rambam are cited by the SHULCHAN ARUCH CM 305:6.) (Y. MARCUS)