307. Leaving Early

45:14 If seven diners ate bread and three diners ate fruit or drank beverages (except water – OC 197:2) in an amount that would require a concluding blessing to be recited, they may form a zimmun of ten and say God’s Name. In circumstances such as this, all authorities agree that even fruit or even a beverage is sufficient to join the zimmun. It is a mitzvah to try to assemble a minyan in order to bentch using God’s Name but if there are only six who ate bread, this does not work as we require a supermajority to have eaten bread. 45:15 All who ate together form a group for bentching, either of three or of ten, and they may not disperse without fulfilling their obligation in zimmun. (According to Mishnah Brurah 193:18, “eating together” means at the same table. Members of a family are considered eating together even without a common table.) This is true even if they did not eat the entire meal together, such as if some joined them later and each ate from his own food. Even if one wanted to finish his meal and go, he may not separate from the group. If two are eating and a third comes later, then if he wants to finish before them and leave, he may separate. He does not join with them to form a group because he neither started nor finished with them. It would, however, be a mitzvah for him to tarry in order to join with them for a zimmun. One may bentch by himself and leave if there are compelling circumstances, including business obligations, but if there is no urgency, one must wait to bentch with the group.