The meal held in honor of a bar mitzva is considered a se’udat mitzva.[2] The main talmudic source is Kiddushin 31a, in reference to a statement by the blind sage, Rav Yosef. He said that if he would be convinced that the blind are obligated in mitzvot, he would make a celebration for his colleagues because one who is commanded in mitzvot receives more reward for his fulfillment than one who is exempt. If a celebration is in place just for finding out that one has always been obligated, all the more so is it appropriate when the obligations begin, when one becomes a bar mitzva. This is certainly so when the party is held on the Jewish birthday itself, the moment that the boy becomes obligated.[3] The Magen Avraham[4] rules that even a bar mitzva meal that is not on the birthday can be considered a se’udat mitzva if the bar mitzva boy publicly says divrei Torah. The apparent logic is that those present are reminded that this boy is indeed involved in the study of Torah, as he is now commanded to be, and they appreciate the cause for the celebration.
It is permitted to partake of meat and wine at a se’udat mitzva even during the week of Tisha B’Av,[5] and this ruling should apply to a bar mitzva as well.[6] Some want to conclude from the Shulchan Aruch’s silence on the matter that he does not allow meat at a se’udat mitzva during the week of Tisha B’Av.[7] However, most poskim are lenient in the matter, even for Sephardim. Although a delayed bar mitzva party with divrei Torah may take place during the Nine Days, it should not be delayed for that purpose.[8]
During the first part of the Nine Days, one may invite to the se’uda whomever he normally would, but people who just happen to be around may not partake of the meat and wine. During the week of Tisha B’Av, one should invite only reasonably close relatives and a small group of friends.[9] Some suggest serving fish and thereby removing the complication this situation raises. Others are lenient with the guest list even on the week of Tisha B’Av,[10] and there is room to rely upon those opinions.
Participants at permitted bar mitzva celebrations at this time may sing, but neither live nor recorded music should be played.
Receiving an aliya to the Torah and the accompanying ceremonies in shul on Shabbat are not problematic.[11]