9. One may not give a friend a gift on Shabbos (1), unless it is an article that he needs for Shabbos (2). Similarly, it is forbidden to give a person an object as collateral for a loan on Shabbos, unless the recipient needs it for Shabbos or it involves a mitzvah. [In these instances,] the giver should not say, "Here is your collateral," but rather should give him the object without comment.
(1) The Sages prohibited any sort of transaction on Shabbos, out of a concern that people may inadvertently come to write something down, which is a biblical prohibition. Giving a gift is included in this prohibition, because it entails a transfer of ownership.
(2) Or for the purpose of performing a mitzvah (Bais Yosef 527). It is preferable not to give a Bar Mitzvah or wedding present on Shabbos (Magen Avraham 306:15), however, Rabbi Akiva Eiger permits sending a gift to a groom. If one does receive a gift on Shabbos, one should have intention not to acquire it legally until after Shabbos. Some authorities permit giving a gift to a Gentile on Shabbos.