For example, if the money was given in units of tens or fives, it can be assumed that the owner of the money counted the coins in groups of tens or fives and erred in his count.

Rav Aḥa, son of Rava, said to Rav Ashi: And if the one who gave the money is a harsh person, who is not accustomed to giving gifts, what is the halakha? Should it be assumed that he made a mistake? Rav Ashi said to him: Perhaps that person once robbed the recipient, and now he included in the calculation the amount he stole, in order to return the stolen money without informing him of the theft. As it is taught in a baraita: One who robs another and then returns the stolen money by including it in the calculation of money paid for another item has fulfilled his obligation to return the stolen money.

Rav Aḥa, son of Rava, asked Rav Ashi: And if the giver was a person from the outside, with whom the recipient had never conducted business, what is the halakha? Should it be assumed that the additional money was given in error? Rav Ashi said to him: Perhaps another person, an acquaintance of the giver’s, robbed the recipient and said to the giver: When so-and-so borrows money from you, include it in the calculation. It is possible that the one who robbed the recipient chose this manner of restoring the latter’s money in order to be spared any shame.

§ Rav Kahana said: I was sitting at the far end of Rav’s house of study, and I heard him say: Gourds, gourds, but I did not know what he was saying, as I did not hear the entire discussion. After Rav arose and left, I said to the students: What is this statement concerning gourds, gourds, that Rav was saying?

They said to me: This is what Rav was saying: If someone gave money to a gardener to purchase gourds from him, and they were going for the price of ten gourds of the length of a span, i.e., the distance between the thumb and the little finger, for a dinar, and the gardener said to the buyer: If you pay me the money now, I will give you gourds a cubit in length at a later point in time, the halakha depends on the circumstances. If gourds of this larger kind are in the possession of the seller, this type of sale is permitted. If they are not in his possession, it is prohibited, as, if he gives him larger gourds at a later date for the price of small gourds, this constitutes interest.

The Gemara asks: Isn’t this obvious? What is the novelty in Rav’s statement? The Gemara answers: The statement is necessary, lest you say: Since they increase in and of themselves it is permitted, as the gardener does not perform any action, but simply waits for the gourds to grow larger before supplying them. Rav therefore teaches us that this is also classified as interest.

The Gemara asks: In accordance with whose opinion did Rav rule? He ruled in accordance with the opinion of this tanna, as it is taught in a baraita: With regard to one who went to milk his goats, or shear his sheep, or extract the honey from his hives, if another found him and the farmer said to him: Whatever milk my goats produce is sold to you, or whatever wool will be sheared from my sheep is sold to you, or whatever honey will be extracted from my hive is sold to you, this is permitted. It is permitted despite the fact that the farmer did not specify precisely how much he is selling, and the buyer may receive more of the product than the current market value would dictate due to his paying for it in advance, as he may also receive less of the product than the current market value would dictate.

The baraita continues: But if the farmer said to him: Such and such an amount of milk from what my goats produce is sold to you, or such and such an amount of wool from what will be sheared from my sheep is sold to you, or such and such an amount of honey from what will be extracted from my hive is sold to you, a transaction of this kind is prohibited, as the farmer is selling him more of the product than the current market value would dictate due to his paying for it in advance. The Gemara states its question: And one sees in this baraita that even though these products increased in value in and of themselves, since they are not in existence at the time of the sale, the practice is forbidden.

The Gemara records another version of this discussion: There are those who say that Rava said: The halakha is that since the sold items grow by themselves it is permitted, as it does not constitute interest. The Gemara raises a difficulty: But isn’t it taught in a baraita that if he specifies: Such and such an amount, it is forbidden?

The Gemara answers that there is a difference between the two cases: There, with regard to milk and wool, they do not increase in and of themselves. This is evident from the fact that if they remove this milk from the goat, other milk replaces it. Therefore, the milk or wool that is generated after the sale is not an extension of the milk or wool that was present at the time of the sale. Conversely, here, in the case of the gourds, they increase in and of themselves, as the same gourds continue to grow. This is evident from the fact that when they remove this gourd from the ground, no other will replace it. Consequently, if he sells him gourds now, any additional growth belongs to the buyer, as the gourds are in his possession from the moment of acquisition.

§ Abaye said: It is permitted for a person to say to another: Take these four dinars for the future delivery of a barrel of wine; if it sours, it is in your possession and you are responsible, but if it appreciates or depreciates in value, it is in my possession, as I accept any loss that results from a change in price. Rav Sherevya said to Abaye: