Answer #3 (Rava): The Mishnah is like R. Oshaya.

(R. Oshaya - Beraisa): Yehudah told Levi 'give me the Maneh you owe me so I can buy wheat'. Levi answered 'I have wheat. I will give you a Maneh's worth of my wheat at today's price.' The price of wheat rose; Yehudah asked for the wheat in order to buy wine.

Levi: 'I have wine. I will give you wine equal in value to your wheat at today's price'. The price of wine rose; Yehudah asked for the wine in order to buy oil.

Levi: 'I have oil. I will give you oil equal in value to your wine at today's price'. In all these cases, it is permitted if Levi has the Peros.

The Mishnah says 'he bought', i.e., with the loan.

(Rava): We learn three things from R. Oshaya:

One may convert a loan into Peros, unlike the Beraisa Rabah brought (62b);

It is permitted only if the borrower has the Peros;

R. Yanai, who says that the Peros are like the money, is correct.

(Rav): Amanah of Peros (Reuven pays Shimon for Peros (at today's price), which Shimon will give later when the price will be higher) is permitted;

Amanah of money (Reuven pays Shimon for Peros (at today's price); later, when the price will be higher, Shimon will pay Reuven the value of the Peros) is forbidden (since he gives and receives money, it looks like Ribis).

(R. Yanai): Getting back their value (in money) is like getting back the Peros. Both are permitted.

Question (against Rav - Beraisa): It is permitted (to receive back money) if Levi has the Peros.

Answer #1 (Rav): The case is, he did Meshichah on the Peros (took them to his premises, at the beginning, therefore, it was no longer like a loan).

Objection: If so, obviously it is permitted!

Answer #2: Rather, he designated a corner of the Peros that will be Yehudah's.

Answer #3 (Shmuel): The Beraisa is R. Yehudah, who permits Tzad Echad b'Ribis (a deal that will end up either like a sale or like a loan).

(Beraisa): Reuven owed Shimon 100; he said that if he does not pay by a certain date, Shimon will get his field. This is permitted only if Reuven eats the Peros in the interim (lest he will pay, and it was always a loan, and Shimon's eating was Ribis);

R. Yehudah permits even if Shimon eats the Peros in the interim.

R. Yehudah: There was a case in which R. Elazar ben Azaryah authorized the buyer to eat the Peros!

Chachamim: No, the seller ate.

Question: What do they argue about?

Answer #1 (Abaye): They argue about Tzad Echad b'Ribis.

Answer #2 (Rava): They argue about whether or not one may take Ribis on condition to return it.

(Rava): Since R. Yanai says that money is like the Peros, we may say that Peros are like money, and we may contract to supply Peros for a set price even if the seller has no Peros (as long as there is a set price in the market).

Question (Rav Papa - Beraisa): It is permitted only if Levi has the Peros.

Answer (Rava): That refers to a loan. I discuss a sale.

(Rabah and Rav Yosef): The reason one may contract to supply Peros even if he has no Peros is because he does not give anything extra to the buyer. Had the buyer kept his money, he could have bought Peros cheaply elsewhere.

Question (Abaye): If so, a loan of a Se'ah on condition to return a Se'ah should be permitted, for the borrower does not give anything extra to the lender It would not have spoiled!

Answer (Rav Yosef): A loan is forbidden. We permit only a sale.

Question (Rav Ada bar Aba): The buyer saves the fee he would have had to pay someone to go to buy where the Peros are cheap!

Answer #1 (Rava): Indeed, it is permitted only when the buyer pays that to the seller.

Answer #2 (Rav Ashi): (In any case buyers need not pay for this.) Donkey-drivers (for the sake of their own employment) go to seek the buyers.

(Rabah and Rav Yosef): If Reuven gave money based on the (low) price of the first grain to reach the market, he must see the seller thresh in the granary.

Question: What is the reason?

It cannot be to acquire it, for seeing is not an acquisition!

Suggestion: It is so the seller will be cursed (He who punished...) if he retracts.

Rejection: He will be cursed even if Reuven does not go to see!

Answer: Really, it is so the seller will be cursed (if he retracts);

Buyers often give money to more than one seller based on the price of the first grain. If he comes to the granary, the seller is assured that the buyer will buy. If he does not come , the seller assumes that the buyer preferred someone else's Peros (so we do not curse him for retracting).

(Rav Ashi): Since this is the reason, the same applies if they met in the market and the buyer said that he expects to receive the Peros.

(Rav Nachman): The general rule of Ribis is that any payment for allowing one to borrow money for a period of time is forbidden.

(Rav Nachman): If wax was selling for four cakes per Zuz, and one seller offered five if the buyer would pay now and receive the wax later, this is permitted only if he has wax now.

Objection: This is obvious!

Answer: The case is, the seller already gave someone else money to receive wax. One might have thought that he is like one who borrows a Se'ah on condition to return a Se'ah, and he already has it at home;

Rav Nachman teaches that this is not so. Since he has not collected his wax, it is as if he does not have it.

(Rav Nachman): If Reuven borrowed money from Shimon and he received more than he was supposed to, if it is an amount that could be a mistake, he must return it. If it is more than that, Shimon intended it to be a gift.

Question: What is an amount that could be a mistake?

Answer (Rav Acha brei d'Rav Yosef): (People usually count ten or five at a time.) If the error is (Rashi - a multiple of) ten or five, he may have skipped counting some groups of ten or five. If not, it is surely an intentional gift.