Winter Vinegar; Date Honey; Milk and Whey

The Mishna states (52a): If a person makes a vow that he will not partake of dates, he can still eat date honey. If he makes a vow not to partake of winter grapes, he may partake of the vinegar made from those grapes. Rabbi Yehudah ben Beseirah says: Whenever a product is called a name that reflects upon its source and a person vows not to partake from that source, he is forbidden to have the product as well. The Chachamim permit this.

The Ra”n asks: Who is this first Tanna? It is neither Rabbi Yosi nor the Chachamim! For we learned above, in the dispute regarding milk and whey, that whenever they called it “whey of milk,” it was forbidden according to everyone! If so, the date honey and the vinegar should be forbidden!

The Rashba answers: The cases are not similar. For in the case of the whey of milk, its form has not been changed. Even initially, when it was mixed with the milk, it was in that very same form. But here it has changed physically.

Furthermore, in the case of whey, the reason it is called “whey of milk,” is because it still has the law of milk. It is not to distinguish it from some other kind of whey, for there is no other kind. But here, when it is called “date honey” or “winter-grape vinegar,” it is not that they still have those laws; rather, it is to distinguish them between other types of honey and vinegar.