Toharot, Chapter Ten, Mishnah Five
1) One who eats grapes out of the baskets or from what is spread out on the ground, even though they burst and dripped into the wine-press, the wine-press remains clean.
2) If he eats the grapes out of a grape-basket or from what was spread out on leaves, and a single berry dropped into the vat:
a) If it has a seal all in the vat remains clean;
b) But if it has no seal, all in the vat becomes unclean.
3) If he dropped some of the grapes and trod upon them in an empty part of the wine-press:
a) If the bulk of the grapes was exactly that of an egg, the contents remain clean;
b) But if it was more than the bulk of an egg, the contents become unclean, for so soon as the first drop came out it contracted uncleanness from the remainder whose bulk is that of an egg.
Section one: The person who is acting in this mishnah is assumed to be impure, for most people are assumed not to preserve their purity. In the first case, since the liquid that comes out of the grapes is not something he desires, it does not render the grapes susceptible to impurity. Even if some of this liquid should burst out and go into the winepress, the other grapes in the winepress remain pure. This accords with Bet Hillel’s opinion in yesterday’s mishnah.
Section two: In this case he takes the grape from a place where if liquid had oozed out, the liquid would render it susceptible to impurity. One grape then falls into the vat. If the grape had a “seal” meaning that the stem from which the grape was plucked from the cluster remained in the grape (this happens to me all the timethen I end up spitting it out), then the other grapes remain pure because we can assume that no liquid came out. When the man touched the grape it was not susceptible to impurity. However, if it had no seal, then we can assume that some liquid had come out and the grape was impure. It would defile the rest of the grapes in the vat.
Section three: In this case, a cluster of grapes falls in a part of the vat that is empty. Then he steps on the grapes. If there is exactly an egg’s volume of grapes then the vat remains pure. When the first drop comes out of the grapes, the cluster now has less than the volume of an egg and food that is less than the volume of an egg does not defile liquid. Even though he defiled the food, the liquid is pure. However, if there is even a little bit more than the volume of an egg, the liquid that is emitted becomes impure by virtue of contact with the impure egg. Then the liquid will defile the winepress, for liquid can defile vessels. This is a similar situation to that found in Toharot 3:1.