Birkat Hamazon for Those Who Have Left the Place of Eating
Question: If I leave my place in the midst of a meal including bread by myself without first bentching (reciting Birkat Hamazon), can I bentch when I remember? If so, how much time do I have to come back to bentch? If I had been eating with two other men and I eventually return before the others have bentched, can I join a zimun with them?
Answer:Your first question is about the ability to come back to bentch where you ate. There is no question that you are able to come back; the major question is whether you are required to come back in order to bentch. Beit Shammai (Berachot 51b) said that if one forgot to bentch at the end of the meal and remembered when he was in a different place, he is required to return to bentch in the original place. Beit Hillel says that he is permitted to bentch where he remembered. The gemara (ibid. 53b) says that if he purposely left the place of eating without bentching, Beit Hillel agrees that he must return. The Shulchan Aruch (Orach Chayim 184:1) cites two opinions among the Rishonim whether we accept Beit Shammai’s or Beit Hillel’s ruling regarding returning after forgetting to bentch and does not give a clear indication of which opinion he accepts. The Mishna Berura (184: 6,7) says that one should return if it is not difficult, and that in any case, it is better to return if he is willing to. If one has bread in the new place and is willing to eat even a small amount of it, he need not return to bentch the original place, as the new place is also a place of eating (Shulchan Aruch ibid. 2).
As far as how long he has to bentch, there is no difference between whether he is in the same place or a different one. The mishna (Berachot 51b) says that one has until the "food has been digested in the intestines." We accept the explanation that this means until a feeling of hunger has begun to return (Berachot 53b; Shulchan Aruch ibid. 5). This depends on how much one ate; it is also difficult to pinpoint the moment. Therefore, we usually work with the assumption is that one has, from the last eating, the amount of time it takes to walk four millin, which most hold is 72 minutes (Mishna Berura 184:20).
There are other significant questions regarding leaving the place of eating. One question is when the person continues eating upon his return. The Shulchan Aruch (OC 178: 1,2) rules that unless one left behind people who continue eating in the original place, there is a break between the returner’s two eating sessions, and he has to first bentch for the first part and then recite a new beracha for the second installment. The Rama (ad loc.) rules that if the food one had eaten is the type that mandates a beracha acharona before he leaves, then the meal continues without additional berachot. It is a matter of debate what is included in that category of food (see Mishna Berura 178:44), but a bread meal certainly is. Still, it is not proper to leave for any extended period from the place of the meal with the intention to return without first bentching without a pressing reason to do so, including the need to perform a mitzva elsewhere (Rama ibid.). Although Sephardim generally accept the Shulchan Aruch’s rulings over those of the Rama, this is an example of the counter rule that one does not recite a doubtfully justified beracha even if the Shulchan Aruch says to recite it (see Kaf Hachayim, OC 174:1; Yalkut Yosef, OC 178:(1)). For a Sephardi, though, it is especially important to leave with the intention to return and continue eating, as this creates a situation where he will not be able to comply with the Shulchan Aruch’s ruling to make new berachot (see V’zot Haberacha pp. 63, 142).
If one ate with others who remain, his connection to the original eating is certainly a strong one (one ramification is that the Shulchan Aruch (ibid.) agrees that he does not require new berachot). There is no question that in such a case, where he had an obligation before he left to join his counterparts for a zimun, he can do so upon returning as well (see the related discussion in the Shulchan Aruch, OC 194:2).