By Horav Yosef Yeshaya Braun, member of the Badatz of Crown Heights
Guests at a Bar Mitzvah celebration often leave a present: a monetary gift of cash or check, a sefer (holy book) or other gifts. Sometimes the gift is clearly demarcated; others, even unlabeled, have a de facto owner by the theory of umdena (logical assessment)—for example, a sefer would likely be intended for the Bar Mitzvah boy himself.
But to whom do the gifts, even the inscribed ones, really belong, the Bar Mitzvah boy or his parents? Perhaps they own all his possessions?
Halachah discusses an adult child—a Bar Mitzvah, is after all, an adult—who is samuch al shulchan aviv (lit., reclines on his father’s table, i.e. is fully supported by his parents). If this “child” comes by a possession, for example, he finds a metziah (an ownerless object), most poskim agree that it belongs to the child.
Rabbenu Tam disagrees, and claims that in this case, the adult child’s metziah belongs to his parents. It is not definitive whether Rabbenu Tam would include a matanah (gift) in the same category as a metziah, or whether it might, in his opinion, belong to the adult child. The consensus among poskim is that ownership is definitely conferred once the adult child is a muchzak (lit., established, i.e., has established ownership by having the item in his possession); by accepting the gift from the giver, the item is his free and clear.
If the gift is in the parent’s possession, there might be place in halachah for them to keep it on the principle of “Kim li!” (lit., “this is my opinion!” i.e. someone who is a muchzak can often rely on a minority halachic decision in his favor).
(It should be noted that parents who rely on Bar Mitzvah gifts to pay for the affair or the child’s Tefillin should discuss this with the child in advance; the Bar Mitzvah boy’s whole-hearted agreement to “share the costs” would cover all possible halachic issues.)