Resources for Kesubos 99
The גמרא says that even if we assume that if you tell a שליח to sell 100 acres of land and they sell 200 acres that the sale of the 100 acres is still valid, we still have a ספק by a case where he tells the שליח to sell 100 acres of land and he only sells 50. The ספק is: is he still considered a שליח since the שליח can say he did him a favor by only selling half of the land since the owner may not need so much cash; or can the seller say I don’t want to sell in parts since I don’t want to have to deal with so many שטרות. There is a מחלוקת ראשונים about each of these צדדים. We will address the first צד of “I’m doing you a favor”. The רא"ש in אות ט"ו says that this claim is לאו דוקא. The שליח doesn’t need to be doing the seller a favor. He just needs to not be hurting him in any way like by being אפושי שטרות. The רא"ש’s proof is that the גמרא tries to prove that the claim of “I’m doing you a favor” is correct from the case of someone who was told to buy a shirt for $6 and he bought a shirt for $3 and a טלית for $3. In that case the שליח cant claimhe did the seller a favor since he didn’t save him any cash. Therefore, it must be that the claim of דטבא לך עבדי לך is לאו דוקא. The נתיבות המשפּט in קפּ"ב ס"ק ט points out that according to the רא"ש if a seller told a שליח to sell something that wasn’t land and the שליח only sold half that amount it would definitely be a valid sale since there is no issue of אפושי שטרות by מטלטלין where a שטר is not used. The נתיבות asks on the רא"ש the following: there is a גמרא in ב"ב דף פּ"ו ע"ב that says that if you tell someone you want to sell a כור and the buyer is being קונה each סאה separately that the seller can back out until the last סאה is נקנה since we assume if he said I’m selling a כור that he needs the cash for the full כור and isn’t willing to sell otherwise. If so, how can the שליח be better? Can’t the seller be חוזר since not all of the sale was completed? Therefore, the נתיבות like the ר"ן’s פּשט in our סוגיא better. The ר"ן says that the שליח can only claim דטבא לך עבדי לך if he has a buyer who would still like to buy the other half. However, if he only has a buyer who is willing to buy half then he can’t say I did you a favor because he wanted to sell the whole thing. The נתיבות suggests that the according to the ר"ן we would answer the question as follows: by the case of a person selling on their own, they can always back out until the last סאה is sold because they only want to sell if the buyer purchases the entire amount. However, by a שליח, we said from the ר"ן that for the שליחות to work it must be that the שליח can find someone else to sell the other half to or else a half sale will be invalid. If so, it makes sense that the seller cannot back out on the half that was sold by the שליח since he is doing him a favor since he now has the option of keeping the cash or selling the other half later. Therefore, the claim of דטבא לך עבדי לך is critical. As to the proof of the רא"ש that דטבא לך עבדי לך must be לאו דוקה from the fact that the גמרא brings a proof from a case of someone who did not save the owner any cash since he spent all the money he was given on the חלוק וטלית, the נתיבות answers that the ר"ן would say that it must be a case where the שליח could sell the טלית and get back a bigger חלוק like he was supposed to buy or everyone would agree its not a valid שליחות. So in that case as well it is a favor for him as well. Therefore, it should come out that according to the רא"ש if the משלח sends the שליח to sell a certain amount of מטלטלין and
he sells half it would definitely be valid since there is no אפושי שטרא, whereas according to the ר"ן it would only be valid if the שליח is able to sell the second half later.
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