If the buyer did not pay but just gave his word that he would buy, he is not subject to the curse.

R. Yaakov bar Zavdi citing R. Yochanan: If a person agreed to give a gift to someone and he wishes to retract, he may retract.

At the time that he agreed, he needs to have said it with full intent to give; but ultimately, if he decided not to give it, he has not transgressed.

We are referring to a poor man, but for a rich man, if he agreed to give a gift to a poor man, it is like a vow.

Rav instructed his servant, "When I tell you to give a gift to someone, if that person is poor, give it to him immediately and do not ask me again about it, since I cannot anyway retract. (However, if that person is rich, do not give him until you have confirmed it with me, as I might have changed my mind.)

R. Yochanan gave gold coins to his relative for oil. The value of oil increased. They asked R. Yanai and he said that on a Torah level, the money acquires; but they said that it does not, to prevent a person from saying (after he received the money but before the buyer took the merchandise) that the buyer's wheat had been burned in a fire in the attic.

R. Shmuel bar Susartai citing R. Abahu: If he claimed that 'your wheat was burned in the attic' - he is believed.

Question (R. Yitzchak): What is the case (of R. Abahu)? If the buyer's money acquired it, it was his wheat that burned (so why believe the seller without an oath - he is like an unpaid watchman on the wheat and should require an oath to exempt himself)?! If not, it was the seller's wheat that burned...? (The question remains unanswered.)

R. Simon citing R. Yehoshua ben Levi: A person who gave his friend ten dinars and told him, "I would like to buy 100 barrels of wine''. If he said, "from this (certain) house'', it is permitted; if he said, "from (next to) this vineyard'', it is prohibited.

Question: What is the difference? In a house, it is not common that the house will fall down (and destroy the contents); in a vineyard, it is common that the vineyard will be burnt (thereby destroying the barrels). (In such a case, it is understandable that we say that the payment did not make the acquisition, because of the danger that the seller might not eventually be able to give the wine. However, there is no such concern in the house, so an acquisition with the money is permitted and the money does not become a loan, thereby avoiding any problem of interest.)

R. Yosi: We learn from here that a person who gave his friend ten dinars and told him that they are payment for 100 barrels of wine (that are located in place where fires are not common), as soon as the seller accepted the money, he is required to supply the buyer with the barrels.

R. Shimon ben Lakish: The pasuk states (Vayikra 25, 14), "...or if he acquired from the hand of his friend'' - we learn from here that taking is required from the hand of your friend but not from the hand of a gentile.

Question: According to R. Shimon ben Lakish, when is a person subject to the curse (if there is no acquisition at all with money)?

Answer (R. Yosi bei R. Bun): It follows this Beraisa - If a person does business based on verbal exchanges, he is (not) subject to the curse of "the One who punished''.

(Mishnah): A prohibition applies to overcharging four ma'ah for the sale of a selah (which is 24 ma'ah), which is 1/6th of the sale price.

Until when may the buyer return the item? As long as he sees the merchant or his relative.

R. Tarfon instructed in Lod that overcharging applies to 8 ma'ah to a selah, which is 1/3rd of the sale price; and the merchants of Lod rejoiced.

R. Tarfon to the merchants: The buyer may return the item the entire day.

Merchants: Let R. Tarfon leave our place. They returned to the words of the Chachamim. (The stringency of allowing the buyer to return it all day outweighed the leniency of overcharging only being prohibited when it is 1/3rd.)

Both the buyer and the seller have a prohibition to over (or under) charge. Just as overcharging is prohibited for a regular person (who is not knowledgeable in business), so too it is prohibited for a merchant.

R. Yehudah: A merchant has no prohibition of overcharging. The 'victim' of overcharging has the upper hand, as he can say, "Give me back my money or give me back that which you overcharged.''

(Gemara) - Rav: The value of 4 to 24 is a requirement for the prohibition, but 3 to 18, even though it is also 1/6th, is not overcharging.

R. Yochanan: There is no such requirement and as long as it is 1/6th, it is prohibited.