Published Summer 2015
The scene is ever so common in Jewish homes. A delicious meal is served and followed by mayim achronim . Then one of the participants of the mezuman proclaims, “ Rabosai mir vellin bentchen ” (Gentlemen, let us recite Birchas Hamazon ), and everyone present responds.
The basic halachos are well known. If three men who have reached the age of Bar Mitzvah eat bread together, they form a “ mezuman. ” One of them, known as the “ mezamein ” is the leader. If there are ten men, “ Elokeinu ” is added by the mezamein between the words “ Nevoraych ” and “ She’ochalnu ”, and by the rest of the group between “ Baruch ” and “ She’achalnu ”.
The Mishna at the beginning of the seventh perek of Brochos  tells us Rule #1 about a mezuman . The food must be kosher. The Mishna lists examples of questionable and prohibited food and explains that a mezuman is not formed, and a brocha is not even recited on such food. The Gemara  explains that the reason is derived from Tehillim , where Dovid Hamelech says, “ Ubotzei’a Boreich Ni’eitz Hashem. ” This passage teaches us that if a thief recites a brocha (on the food he has stolen), the act blasphemes Hashem . If one knowingly eats something non-kosher, even if the food is only rabbinically prohibited, there is no mezuman and a brocha is not recited before or after consumption. Blessings are recited only over kosher food.
I. What Must Be Consumed?
All three men who are present are not required to eat bread; only two thirds (i.e., known as a “ rubah deminkra ”, a noticeable majority) is necessary. This means at least two men must eat a kezayis of bread, an amount that obligates them in Birchas Hamazon . The third participant only has to eat a kezayis of any food. Any type of food, including cake, fruit, vegetables or even candy will suffice provided that one eats enough to require a brocha acharona . Alternatively, the third person can drink a revi’is  of any beverage (other than water or seltzer).
II. Eating Together
Once three people eat together, they may not “break up” and recite Birchas Hamazon without a mezuman . Similarly, if ten men eat together, they may not break up into smaller groups that cannot say “ Elokeinu ”. If necessary, six people who ate together are allowed to split into two groups. The same applies to 7-9 people; 20 or more people can also break up, if necessary. A group of 10-19 people may not split.
In general, once one eats with others he has an obligation to join the mezuman and he cannot recite Birchas Hamazon without a mezuman . However, when necessary, if before sitting down to eat a person says that he has in mind not to formally join the group at the table (e.g., at a wedding), he can recite Birchas Hamazon without a mezuman before the rest of the group recites Birchas Hamazon with a mezuman .
Better yet, under the following conditions he can lead the mezuman before others are ready to recite Birchas Hamazon . If three men eat a meal and one of them is ready to recite Birchas Hamazon before the others finish their meal, the other two men may stop and respond to him. To do so, they should not talk or continue eating until he finishes the first brocha ( Hazan Es HaKol ). If two men are ready to recite Birchas Hamazon , the third person who is still eating must stop and answer the mezamein . If two “new” people now sit down with the fellow who answered the mezuman , and the three of them eat a kezayis of bread together, another zimun can be made.
If the group occupies two or more tables, a mezuman is formed if they see each other and are part of one group, such as one family, one yeshiva , or any group that has come together to eat (e.g., a simcha ). A mezuman of three men can be formed in a car, bus, train or airplane. However, “ Elokeinu ” is not added if ten men are in transit together.
If two men who ate bread together finished eating and continued to talk (i.e., they did not end the meal), and then a third man walks in and eats bread (or anything else), a mezuman has been formed even though they did not “eat together”. Since the original two men could have eaten with the latecomer had they desired to do so, this constitutes eating “together”. However, if the two men had already washed mayim acharonim  before the third person came and ate, there is no mezuman as one may no longer eat after washing mayim acharonim . Therefore, we do not consider them as having eaten “together”.
If three men ate bread and one of them forgot that there is a mezuman and recited Birchas Hamazon , one of the two remaining men can still lead the mezuman before he says Birchas Hamazon . The other two men (including the one who already recited Birchas Hamazon ) respond. However, if only two men ate bread and one ate or drank something else, and any one of them forgot and recited the necessary brocha acharona , it is too late to say Birchas Hamazon with a mezuman .
A mezuman should not be formed (i.e., three men should not sit together) at the seudas hamafsekes on erev Tisha B’Av (that falls on a weekday). At a seudas havra’a , the availim should l’chatchilah not sit together to form a mezuman . Availim can form a mezuman .
III. Someone Who Did Not Eat
If someone does not eat or drink anything and is in the presence of three men who have formed a mezuman , he can still answer “ Yehi shaim Hashem …” Then, when the mezamein says “ Nevoraych sheachalnu mishelo ,” this fourth person who did not eat should say the following (i.e., a different nusach than those who ate), “ Baruch umevorach shmo tamid l’olam vaed .” Similarly, if there are ten men answering, an “11th person” present who did not eat should respond “ Baruch Elokeinu u’mevorach shmo …”
IV. The Mezamein (Leader)
Ideally, the mezamein holds a cup ( kos ) of wine (or grape juice) when leading the mezuman . After completing Birchas Hamazon , a Borei Pri Hagafen is recited and he drinks from the cup. It is mehudar to drink a revi’is , however, one is yotzai even if he only drinks a small amount from this “ kos shel brocha ” (cup over which the blessing was recited). L’maaseh , the prevalent minhag at most meals is not to recite Birchas Hamazon on a kos . Nonetheless, many have a kos when there is a minyan or at a seudas mitzvah . Some also use a kos on Shabbos and Yom Tov .
Although women do not form a mezuman , if they eat together with a mezuman of men they must answer the mezamein . If they are too busy to say Birchas Hamazon at that time, they should answer the mezamein thereby participating in the mezuman and then recite Birchas Hamazon later.
The minhag of Ashkenazim is that all three (or 10) members of the mezuman must be Bar Mitzvah . Sfardim allow one of the three (or 10) men to be as young as 9 years old. If an Ashkenazi eats at the home of Sfardim , and the mezuman consists of a Sfardi over the age of Bar Mitzvah , a 9-year old Sfardi and the Ashkenazi, the Ashkenazi can participate but cannot be the mezamein .
Technically, the baal habayis  can ask whomever he wants to be the mezamein . It is praiseworthy to honor any of the following individuals to lead Birchas Hamazon : a guest, a Talmid chochom , a kohen , a Levi , one who has yahrzheit or who is in the 12 months of aveilus .
Sefer Shoshanim L’Dovid  asks why we say in Birchas HaTorah “ Barchu es Hashem ”, yet during a mezuman with a minyan we say “ Elokeinu” , a different name of Hakadosh Boruch Hu ? He answers that the name “ Elokeinu ” signifies din /judgment, and the name of Hashem that we recite signifies rachamim /mercy. When we learn Torah , it is a shaas rachamim (time of mercy). However, when we eat it is a time of din /judgment. Indeed, when a mezuman is formed and there is a “public” display of praising the Ribbono Shel Olam , this zechus allows all of those present to receive a favorable judgment for parnassah , brocha and hatzlacha .
 Or “ Rabbosai Nevoraych ”
 The ancient custom was that the mezamein was motzi all those present by reciting the entire Birchas Hamazon out loud. Today, the custom is that each person “answers” the mezamein at the beginning and then recites Birchas Hamazon by himself quietly.
 The custom of Sfardim regarding boys under Bar Mitzvah is addressed in Section IV.
 The same applies to any hamotzi item (e.g., matzah ) upon which Birchas Hamazon is recited.
 The full text of the mezuman is found in any siddur or “ bentcher ”.
 It is proper for the one who leads the mezuman to also recite the entire first brocha (through Hazan es hakol ) out loud, while everyone else recites it quietly with him, Shulchan Aruch Orach Chaim (hereafter abbreviated S.A. ) 183:7. [See Sefer Zimun K’hilchasa pg. 13, which discusses the basis of those who do not recite the first brocha out loud.] Furthermore, after the participants complete each brocha , the mezamein says the end of the brocha out loud for everyone to hear and answer “ Amen” . Note that sections of Yaaleh v’yavo recited out loud in shul should not be recited out loud during Birchas Hamazon , as the participants cannot answer “ Amen ” in the middle of Birchas Hamazon (whereas in shul , they are allowed to answer “ Amen ” during chazaras hashatz ).
 There is an inyan to briefly rise when saying “ Elokeinu ” ( Eishel Avraham -Buchech 192:1), as long as it can be done without spilling the wine.
 This perek , which begins on Daf 45a, is dedicated primarily to the halachos of Birchas Hamazon and mezuman .
 Also found in Bava Kamma 94a
 Tehillim 10:3
 S.A. 196:1 and Mishna Brura ( M.B. ) Seif Katan ( S.K. ) 3.
 If one inadvertently ate non-kosher food, he should recite Birchas Hamazon (or an after- brocha , depending upon what he ate). However, he may not be counted as part of a mezuman ( M.B. 196:4). If a choleh sheyaish bo sakana (someone with a life-threatening illness) needs to eat non-kosher food, he should recite brochos and he can be part of a mezuman ( S.A. 196:2).
 This is true even if more people ate other food. For example, a mezuman is formed if two men ate bread and six men ate fruit. The two still constitute a noticeable majority of the minimum requirement of three.
 This means that the kezayis must be consumed b’kday achilas pras . Therefore, one must consume 1.33 fl. oz. (40 ml) of food ideally within a span of 2 minutes, but b’dieved even within a span of up to 4 minutes.
 However, he may not be the mezamein . He recites his brocha acharona after answering “ Amen ” to “ Hazan Es Hakol ”, M.B. 183:28. See Chazon Ish Orach Chaim 30:2, who disagrees and says one may recite a brocha acharona immediately after answering the mezamein .
 The third person should drink at least a revi’is , 4 fl. oz. (118 ml), within 30 seconds. The Biur Halacha (197:2 sheyaish bo ) says one can possibly be maykil if the third person drank a “ rov revi’is ” – slightly larger than half a revi’is (2.1 fl. oz.).
 This is the opinion of the S.A. (197:2); others allow water. For further discussion, see M.B. 197:12 and Sefer Zimun K’hilchasa pg. 10.
 Seven is the minimum number that constitutes a “ rubah d’minkra ”, i.e., two-thirds of 10.
 This means that at least seven men must eat bread to recite Sheva Brochos . The other three who eat or drink something else cannot lead Birchas Hamazon , but they could recite sheva brochos . There are other requirements for Sheva Brochos beyond the scope of our discussion (e.g., panim chadashos , etc.).
 See Igros Moshe Orach Chaim 1:56, who says “ Yomru b’feirush kodem..she’ayn mischavinl’hitztaraph .” This heter is for when he has a need to leave before Birchas Hamazon because the meal is lengthy (e.g., a wedding, when it is difficult to stay until the end) or due to another davar nachutz ( important matter). See Ba’er Moshe 3:32 who adds that one should ideally also begin eating before or after the others at the table, thereby not forming k’vius with them.
 In such a case, if three men are ready to recite Birchas Hamazon , they may make a mezuman . At a wedding, if ten men are ready to recite Birchas Hamazon early, if they make a mezuman they would need to also recite Sheva Brochos , which may prove to be impractical.
 If they do not want to interrupt their meal, they are not required to stop and he will have to wait to recite Birchas Hamazon . Furthermore, if it is not urgent it is not derech eretz for one person to ask two individuals to stop their meal unless he assumes that they will not be makpid . A son must stop for a father and a student for his rebbi ( Shaarei Teshuva Siman 200).
 See S.A. and Rama siman 200:1 & 2.
 M.B. 193:33. Also see M.B. 200:9, who discusses this case and an array of similar cases concerning a mezuman of three or ten.
 M.B. 193:18.
 HaRav Moshe Heinemann, shlit”a , noted that it is said in the name of HaRav Aron Kotler, zt”l that individuals eating in a yeshiva dining room at a time set by the administration form a mezuman , even if they are eating at different tables, as long as they see each other. This is true both on Shabbos and during the week. A similar opinion is found in Minchas Yitzchok (8:8:3). For a full discussion, see Sefer V’zos Habracha Chap. 14 which quotes additional opinions on this issue.
 In a restaurant, if two men are at one table and two men are at a different table, there is no mezuman ( Minchas Yitzchok 8:8:3). However, if three men are at one table and form a mezuman , individuals at other tables may respond (see Piskei Teshuvos 193:7).
 M.B. 193:26
 See S.A. 197:1
 According to some opinions, they can no longer form a mezuman with a third person even if they simply said, “Let’s bentch ” (see Biur Halacha 197, “ Aval im …”).
 See Rama 197:1. Similarly, a mezuman is formed if two men ate meat and one ate dairy. In such a case, the custom is for the one who ate dairy to lead the mezuman because he is able to also eat meat. See M.B. 196:9, who also discusses cases where the dairy is hard cheese.
 Thus, the two people who recite Birchas Hamazon are yotzai zimun . The one who forgot is not yotzai zimun (“ parach zimun minay ”).
 In other words, either of the following inadvertently occurred without a mezuman : One of the men who ate bread recited Birchas Hamazon , or the one who ate other food or drank recited the necessary brocha acharona . In either case, there is no mezuman .
 See Rama 197:1
 The meal the mourners eat after a funeral.
 Gesher Hachaim 2:18:1, if they did sit together at the seudas havra’a they would bentch b’mezuman (without “ Elokeinu ”, even if there are ten men). See Shach Yoreh Deah 379:6.
 Shulchan Aruch Yoreh Deah 379:6
 If he drinks water, although he is not mitztaref to the mezuman , he can still respond like those who ate. See Aruch Hashulchan (198:2).
 If he came in as they were already responding “ Baruch Sheachalnu ” – he should simply respond “ Amen ”.
 If this 11th person just had something to drink, see M.B. 198:1.
 If he is at a Sheva Brochos and did not eat, he should respond, “ Boruch Elokeinu u’mevorach shmo tamid l’olam vaed shehasimcha b’mono ” ( M.B. 198:6). Likutei Maharich ( Seder Birchas Hamazon ) says to insert “ shehasimcha b’mono ” after saying “ Elokeinu ”.
 It is a mitzvah min hamuvchar to have a kos ( S.A. 192:1).
 The cup must hold at least a revi’is (3.8 fl. oz.) and in general is similar in halacha to a cup used for Kiddush (full, etc.).
 The custom is to hold the cup up through “ Al Yichasraynu ” ( Ktzos Hashulchan 46:f21).
 If it is after sunset at the end of Shabbos or Yom Tov , one does not drink from the cup (unless it is Sheva Brochos ). The custom in many shuls is to save it for havadala .
 Igros Moshe Yoreh Deah 3:52:3.
 Of course, a kos is required at Sheva Brochos and it is customary at the seuda of a bris (each of these occasions has a special nusach as printed in most bentchers ). A kos is also required at the seder on the first two nights of Pesach (even if there are less than three men, and the “mezuman nusach” is not recited).
 See Biur Halacha 199:7, “ Nashim …ach haolam lo nahagen kayn .”
 See S.A. 199:7 and Biur Halacha “ V’yotzos … elah …” For further discussion, see Piskei Teshuvos 199:f9.
 Rama 199:9
 See S.A. 199:9 and M.B. S.K. 24; however, the 9-year old cannot lead the mezuman. He can lead only after his Bar Mitzvah .
 See Sefer V’zos Habrocha Chapter 14.
 When a guest leads bentching , the custom is to add the words “ Birshus Baal Habayis ”. Additions of “ Birshus Harav ” or “ Birshus Hakohain ”, etc. are added when relevant.
 See Sefer Ktzos Hashulchan siman 45 in the Badei Hashulchan end of oys 42 in the name of the Levush .
 See S.A. 201:1, who notes that the guest should also recite the Yehi Ratzon insertion as a special brocha for the host. See Seder Birkas HaMazon (Dayan Raskin, London 5774) , excerpt from forthcoming edition of Siddur Rabeinu Hazaken im Tziyunim Mekoros ve’Heoros , pgs. 50-51 for an explanation as to why the nusach was not found in most earlier siddurim and why some are not noheg to say it.
 For more detailed specifics regarding which of the above takes precedence, see S.A. 201 and the various nosei keilim on the siman .
 Brochos 7:3