It is understood from his statement, “the sale of date pits within dates,” that if the pits are removed from the dates and then sold, the sale is valid, because they are known.

His statement, “or wool on an animal’s back”: this is due to a hadith prohibiting it (1), and because it is part of the animal or connected to it. Thus, it may not be sold, just as it is impermissible to sell a part of an animal—for example, if one were to sell its hand or leg. Moreover, it may increase, so the increase would be unknown. Thus, we have one textual proof and two underlying rationales.

An example is a man who owns a sheep. Someone who spins wool comes to him and says, “Sell me the wool on your sheep.” If he sells it to him, this is not permissible (2).

The second view is that it is valid to sell wool while it is still on the animal’s back, on condition that it be shorn immediately and that the animal not be harmed thereby. This is because it is visible and known, and there is nothing to prevent its sale; thus, the sale entails no prohibited element. This view is correct, because if it is sold on condition that it be shorn immediately, it is like selling crops on condition that they be cut immediately. Any growth that may occur is eliminated by stipulating that it be shorn immediately.