Bava Batra, Chapter Six, Mishnah Three
Mishnah three discusses rules concerning the sale of wine.
1) If a man sold wine to his fellow and it turned sour he is not responsible. a) But if it was known [to the seller] that his wine would [soon] turn sour, this is a mistaken purchase. 2) If he had said to him, I am selling you spiced wine, he is responsible for its remaining [good] until Shavuoth. 3) [If he said] it is old wine, it must be from last years. a) [If he said] it is vintage old wine, it must be from the year before last.
This mishnah is concerned with the responsibility of a wine seller to ensure the quality and preservation of the wine which he sells. If he sold him wine and it turned sour, the seller is not in general responsible, since wine is known to turn sour. If, however, the seller knew that the wine would soon turn sour and he did not warn the buyer, the seller is responsible to return the buyers money. If he sold him spiced wine, he is responsible that it not turn sour until Shavuoth. Spiced wine was known to last during the winter but turn to vinegar due to the heat of the summer. Therefore the wine need only last until Shavuoth, the holiday celebrated at the beginning of the summer. Finally the mishnah clarifies two terms used in the selling of wine. Old wine must be from last years batch and vintage old wine must be from the year before last. If the seller promised one of these types of wine and he gave the buyer wine that was not as old, the buyer can demand his money back.