Bava Kamma 103A

אין כופין את המוכר למכור זימנא אחריתי. ואם אמר לו: ״על מנת״⁠ – כופין את המוכר למכור.

the seller is not compelled to sell the field another time, i.e., to provide the purchaser with a document denoting him as the owner of the field. But if he said to him: I will purchase the field on the condition that you will provide a deed in my name, the seller is compelled to sell the field again, i.e., to provide the purchaser with a document denoting him as the owner.

אמר מר: הלוקח שדה בשם חבירו ⁠– אין כופין את המוכר למכור זימנא אחריתי. פשיטא! מהו דתימא, מצי אמר ליה: מידע ידעת דאנא לנפשאי שקילנא ⁠– ופנחיא בעלמא הוא דקבעינא, וזוזי בכדי לא שדינא, אלא אדעתא דכתב ליה שטרא אחרינא; קא משמע לן דאמר ליה: עניינא עבדי לך בהדי ההוא דזבנת ליה בשמיה, ויכתוב לך שטרא אחרינא.

The Talmud clarifies the baraita: The Master said: In the case of one who purchases a field in the name of another, the seller is not compelled to sell the field another time. The Talmud asks: Isn’t this obvious? The Talmud answers: Lest you say that the purchaser can say to the seller: You knew that I took, i.e., purchased, the field for myself, and it was merely for protection [ufanaḥya] that I desired to obtain ownership by claiming to purchase it in the name of the other person, and I do not throw out money for naught. Rather, it was with the intention that you will write another document for him, i.e., the seller, stating that I purchased the field. The baraita therefore teaches us that the seller can say to him: I have performed a matter for you together with the one in whose name you purchased the field, and let him write you another document.

ואם אמר לו ״על מנת״⁠ – כופין את המוכר למכור. פשיטא! לא צריכא, דאמר להו לסהדי קמיה דידיה: חזו דשטרא אחרינא קא בעינא. מהו דתימא, מצי אמר ליה: אמינא, שטרא מהיאך דקא שקלת בשמיה קאמרת; קא משמע לן דאמר ליה: להכי טרחי ואמרי להו לעדים קמך, דמינך הוא דקא בעינא.

The Talmud discusses Abaye’s interpretation of the latter clause of the baraita, which states: But if he said to him: I will purchase the field on the condition that you will provide a deed in my name, the seller is compelled to sell the field again. Isn’t that obvious? No, it is necessary to state this halakha in a case where the purchaser said to the witnesses in front of the seller: You can see that I require another document. Lest you say that the seller can say to him: I thought that it was a document from the one in whose name you purchased the field that you were saying you required, and not from me. Therefore, the baraita teaches us that the purchaser can say to him: It was for this that I took the trouble and said to the witnesses, in front of you, that I require another document, as it is from you that I require the document.