Question: If I want to leave a chasuna early, what do I do about bentching with a mezuman?
Answer: There are two potential issues with leaving a chasuna early. The first is whether one who is part of a large gathering can bentch without a mezuman of ten.
The Shulchan Aruch (OC 193:1) writes that one eating along with nine other men must not leave early and bentch with a smaller mezuman without a minyan. The Mishna Berura (200:5) writes that if one really needs to leave early, it is best if he makes a zimun with two others.
The second issue is whether one can miss the sheva berachos that are recited after bentching.
R’ Yitzchak Yaakov Weiss (Minchas Yitzchak 2:43:15) writes that while sheva berachos needs to be recited at the meal, that doesn’t mean everyone needs to participate. The Gemara and poskim make no mention of staying as they do for bentching. Thus, one who can’t stay until the end may leave early. R’ Eliezer Waldenberg (Tzitz Eliezer 11:84) agrees, writing that only those who participate in the bentching together with a zimun of ten are obligated to join in with the sheva berachos. It would be wrong, though, to gather a minyan to bench and say the sheva berachos without the chassan and kallah.
R’ Moshe Feinstein (Igros Moshe OC 1:56) writes, however, that everyone who participates in the meal is obligated to participate in the sheva berachos. Thus, one who doesn’t want to stay until the sheva berachos must stipulate before they eat that they don’t want to be included with everyone else and that they want to eat and bentch alone. Accordingly, one would bentch without a mezuman.
R’ Moshe Stern (Be’er Moshe 3:32) argues that the obligation to join in for sheva berachos only applies when the chassan and kalla are bentching, and not earlier. He challenges the basis for making such a stipulation, and suggests that one should rather ensure that he washes after the others, so that he isn’t starting to eat together with everyone else. Even if one does this, one would be allowed to make a mezuman, preferably with a minyan, but otherwise with just two others.In conclusion, it is ideal if one can bentch with a mezuman of ten. If one knows that they need to leave early in advance, it is best to stipulate in advance that one doesn’t want to participate in the communal meal and wash at a different time. One who didn’t make this stipulation and needed to leave, could make a mezuman, even with two other men if necessary.