How much legal significance does a document delineating a gift have?
According to the baraita quoted by our Gemara, Rabban Shimon ben Gamliel rules that if someone gave a present to his friend by means of a shetar matana – a document that delineates the gift – if the document is returned to the first person, the gift is returned to him, as well. The Ḥakhamim say that the gift remains the property of the recipient.
Rabba explains this difference of opinion as being based on the question of whether or not otiyot niknot be-mesira – literally whether “letters are purchased by transferring them.” Essentially the question is whether transferring a note or contract is sufficient to effect a transaction or if there is a need for a kinyan – a formal act of ownership to take place. According to Rabban Shimon ben Gamliel, otiyot niknot be-mesira, so the gift will be given or returned with the transference of the shetar matana. The Ḥakhamim who disagree believe that once the gift is given and the recipient takes possession of it, transferring the shetar matana to another has no meaning.
The R”i MiGash believes that this question only applies to cases where the transfer of the gift was effected solely by means of the shetar matana, with no other kinyan having been done. If, however, there was an associated kinyan that took place, then the role of the shetar was merely to serve as a proof of the transaction, and even Rabban Shimon ben Gamliel would agree that returning the shetar would have no effect on the gift. The Ramah disagrees, arguing that according to Rabban Shimon ben Gamliel the shetar becomes a powerful proof of ownership for the person who is holding it, to the extent that it is possible to suggest that transferring the shetar would be equivalent to transferring the property that it represents.