Kiddushin 27A

נתון לו ליהושע, ומקומו מושכר לו. ועישור אחר שאני עתיד למוד נתון לו לעקיבא בן יוסף, כדי שיזכה בו לעניים, ומקומו מושכר לו. שמע מינה בעינן צבורים בה! שאני התם, כי היכי דלא ליטרחינהו.

is given as first tithe to Yehoshua ben Ḥananya, who was a Levite, and the place of the tithe is rented to him so that he can acquire the tithe by means of the land. And another tenth that I will measure out in the future as the poor man’s tithe is given to Akiva ben Yosef so that he will acquire it on behalf of the poor, and its place is rented to him. One can learn from here that we require the movable property to be piled on the land, as Rabban Gamliel emphasized: Its place. The Talmud rejects this argument: It is different there, as Rabban Gamliel did this so as not to trouble the rabbis to whom he was giving the tithes by forcing them to transport the tithes to a different location. For reasons of convenience he transferred to the other rabbis ownership of the land where the tithes were already situated.

תא שמע, דאמר רבא בר יצחק אמר רב: שני שטרות הן: ״זכו בשדה זו לפלוני וכתבו לו את השטר״⁠ – חוזר בשטר, ואינו חוזר בשדה. ״על מנת שתכתבו לו את השטר״⁠ – חוזר בין בשטר בין בשדה.

The Talmud further suggests: Come and hear a solution for this dilemma, as Rava bar Yitzḥak says that Rav says: There are two types of documents. If one says: Acquire this field for so-and-so and write the document for him as proof of the sale of the field, he can retract his agreement with regard to the document. He can change his mind and tell them not to write the document. But he cannot retract his agreement with regard to the field, as the buyer has already acquired it. By contrast, if he said: Acquire this field for so-and-so on the condition that you write him a document, if the document has not yet been given he can retract his agreement both with regard to the document and with regard to the field, as he transfers the field to him only on the condition that he writes a document.