Bava Metzia 48A

רבי שמעון אומר: אף על פי שאמרו טלית קונה דינר זהב ואין דינר זהב קונה טלית, מכל מקום כך הלכה. אבל אמרו: מי שפרע מאנשי דור המבול ומאנשי דור הפלגה ומאנשי סדום ועמורה וממצרים בים ⁠– הוא עתיד ליפרע ממי שאינו עומד בדיבורו.

R' Shimon says: Even though the rabbis said that when one party takes possession of a garment, the other party acquires a gold dinar, but when one party takes possession of a gold dinar, the other party does not acquire a garment, in any case, that is what the halakha would be. But the rabbis said with regard to one who reneges on a transaction where one party pulled the gold dinar into his possession: He Who exacted payment from the people of the Generation of the Flood, and from the people of the Generation of the Dispersion, and from the inhabitants of Sodom and Gomorrah, and from the Egyptians in the Red Sea, will in the future exact payment from whoever does not stand by his statement.

והנושא ונותן בדברים ⁠– לא קנה, והחוזר בו ⁠– אין רוח חכמים נוחה הימנו.

The baraita concludes: And one who negotiates, where the negotiation culminates with a statement committing himself to acquire the item, did not acquire the item without a formal act of acquisition. But with regard to one who reneges on his commitment, the rabbis are displeased with him.

ואמר רבא: אנו אין לנו אלא ״אין רוח חכמים נוחה הימנו״. דברים ואיכא בהדייהו מעות ⁠– קאי ב״אבל״. דברים וליכא בהדייהו מעות ⁠– לא קאי ב״אבל״.

And Rava says: With regard to one who reneges on his commitment, we have only the statement that the rabbis are displeased with him, but not that he is subject to a curse. The Talmud explains: If there is a statement of commitment and there is the payment of money accompanying it, he stands subject to the curse: But the rabbis said: He Who exacted payment. If there is a statement of commitment and there is no payment of money accompanying it, he does not stand subject to the curse: But the rabbis said: He Who exacted payment.