פירוש על קידושין 53:3

R. Hiyya b. Abin adds in another type of document—one which the seller writes before the sale even occurs. In this case, once he transfers the land, the deed belongs to the buyer no matter where it is. This seems to prove that the movables (in this case the deed) need not be on the land, for the seller has transferred ownership of the field and through it he has transferred the document as well.
The Talmud rejects this as proof—the deed is like the land. It is not a different type of movable, like sheep or barrels. The deed is not transferred by being connected to the land—it simply is part of the transaction of the land.