1) RAV'S OPINION IN THE CASE OF WINE THAT QUICKLY TURNS TO VINEGAR
OPINIONS: The Gemara discusses a case in which a person buys a barrel of wine and it turns into vinegar. Rav rules that if it turned into vinegar within three days of the purchase, this is a clear indication that it had already started to turn into vinegar when it was still in the possession of the seller, and thus the seller is liable. If it turned into vinegar after three days from the purchase, this is a clear indication that it started to go bad only when it was in the possession of the buyer, and thus the seller is not liable.
Is the Gemara discussing a case in which the buyer did not check the wine inside the barrel at the time of the purchase to determine that it had not started to turn into vinegar, or a case in which the buyer inspected the wine at the time of the purchase, but for some reason failed to notice that the wine was going bad?
(a) The RASHBAM (DH Amar Rav) writes that even if the buyer tasted the wine before he bought it and did not think that the wine was going bad, the fact is that when wine turns into vinegar, that process must have started three days earlier. This means that the sale is a Mekach Ta'us, since the buyer intended to buy regular wine and not wine that was going bad. This is also the opinion of the CHOCHMEI TZARFAS. (See also RI in TOSFOS to 96b, DH Shmuel.)
(b) The ALIYOS D'RABEINU YONAH explains that the buyer did not taste the wine at the time of purchase. If he did taste it and he found that it tasted fine, it must be that the wine started to go bad only later. It is not reasonable to assume that Rav maintains that a buyer who accepts the wine to his satisfaction is entitled to a refund because the wine's change to vinegar was undetectable at the time of purchase.
(c) The RASHBA quotes others who explain that when Shmuel says that the wine turned bad because it was transported, he does not mean that it was transported in its barrel, but rather that the buyer poured the wine into a different barrel. Such a procedure can cause wine to go bad, as the verse says, "It was not poured from one vessel to another, therefore its taste was maintained" (Yirmeyahu 48:11). Rav, however, maintains that even when the wine was poured into a different barrel, it is assumed that this was not what caused the wine to go bad when it happened within three days of when the wine turned into vinegar. It must have already been on its way to becoming vinegar exactly three days earlier. (Y. Montrose)
96b----------------------------------------96b
2) SHMUEL'S OPINION IN THE CASE OF WINE THAT QUICKLY TURNS TO VINEGAR
OPINIONS: The Gemara discusses a case in which a person buys a barrel of wine and it turns into vinegar. Shmuel rules that even if the wine turned into vinegar within three days, which usually indicates that the wine had started to go bad in the possession of the seller, the seller may say to the buyer that the wine turned bad only as a result of being carried on the buyer's shoulder. What does this mean?
(a) The Rashbam (96b, DH u'Shmuel) explains that when Shmuel says that the wine turned bad "when it was being carried on the buyer's shoulder," he means that the wine turned into vinegar only because of the sins of the buyer, and it did not turn into vinegar in the possession of the seller.
The RASHBA has difficulty with this explanation. If Shmuel's intention is to say that the inauspicious Mazal or the sins of the buyer caused the wine to go bad, Shmuel should say instead, "Mazlei Garam" -- "his sins caused it." Why does he use a cryptic phrase that "wine on the shoulder of a person jumps (goes bad)"? Moreover, how does the Rashbam understand the rulings of Rav Yosef, who rules like Shmuel in the case of wine that goes bad, but like Rav in the case of beer that goes bad? If a person's sins can ruin wine, they should also be able to ruin beer!
Some answer that sins ruin specifically wine and turn it into vinegar, as the Gemara later (98a) implies. The Rashbam there (DH she'Ne'emar) explains the Gemara's statement that a haughty person's wine goes bad because of "Midah k'Neged Midah." Just as a haughty person pretends that he is something important and he really is not, the haughty person's wine turns into vinegar, showing that he really is not the important person he pretends to be. This analogy does not apply to the spoilage of other beverages.
(b) The CHOCHMEI TZARFAS (see RI in TOSFOS to 96b, DH u'Shmuel) explain that Shmuel maintains that although most wine which has turned into vinegar started to go bad three days earlier, it is possible that when the wine is transported by the buyer it turns bad due to the rigors of being transported. The seller therefore cannot be faulted for selling bad wine.
There appears to be a clear practical difference between the way the Rashbam understands the ruling of Shmuel and the way the Chochmei Tzarfas understand his ruling: a case in which the sale was consummated but the wine was not subjected to any transport. According to the Rashbam, Shmuel's ruling still applies; it is the buyer's responsibility if the barrel is opened within three days and found to contain vinegar. According to the Chochmei Tzarfas, Shmuel may agree in this case that the seller is responsible, since there is no way to prove that the wine did not start going bad when it was still in his position.
(c) The RASHBA quotes others who explain that when Shmuel says that the wine turned bad because it was transported, he does not mean that it was transported in its barrel, but rather that the buyer poured the wine into a different barrel. Such a procedure can cause wine to go bad, as the verse says, "It was not poured from one vessel to another, therefore its taste was maintained" (Yirmeyahu 48:11). Rav, however, maintains that even when the wine was poured into a different barrel, it is assumed that this was not what caused the wine to go bad when it happened within three days of when the wine turned into vinegar. It must have already been on its way to becoming vinegar exactly three days earlier. (Y. Montrose)