One of the halakhot we noted last week, that we need not repeat birkat hamazon if we forget `al hanisim, raises the issue of which mentions of a day must be included in birkat hamazon. In Orah Hayyim 188;6, the Shulhan Arukh rules that if we forgot to mention Shabbat or Yom Tov (meaning holidays ordained by the Torah) in the course of birkat hamazon, we have an opportunity to mention the relevant day before beginning the fourth berakhah of birkat hamazon, hatov ve-hametiv. Having finished bone yerushalayim but not having started the next berakhah, we can insert another berakhah in our ordinary birkat hamazon, which refers to the forgotten day (the text of those berakhot is too lengthy to include here, but is worth memorizing for such occasions; at the very least, it is worth owning a birkon that includes the text of those berakhot).

Once we start the fourth berakhah of birkat hamazon, we would have to repeat the entire prayer, in order to include the proper mention of the day. This halakhah does not apply to Rosh Hodesh, when we also say ya`aleh ve-yavo, and could also insert a special berakhah before hatov ve-hametiv if we forgot. Once we start hatov ve-hametiv in that situation, we have simply lost the opportunity to mention Rosh Hodesh in the body of our birkat hamazon.

We can explain the distinction between Shabbat and Yom Tov on the one hand and Rosh Hodesh on the other by noting (as others have) that there is no specific obligation to eat a meal with bread on Rosh Hodesh, whereas such an obligation does exist on Shabbat or Yom Tov. Since the Rosh Hodesh meal is voluntary, there is no inherent connection between the day and the meal; if we forget to connect that meal to that day, therefore, we have not lost the value of the prayer. On Shabbat and Yom Tov the day requires the consumption of this meal, so that without mentioning the day, we have not properly connected our eating to the reason that brought it about.

Since it is the obligation to eat a meal with bread that makes ya`aleh ve-yavo indispensable, Magen Avraham (cited by Mishnah Berurah, siman katan 26) noted that if someone ate extra, voluntary, meals on these days—more than a meal at night and during the day— forgetting ya`aleh ve-yavo at those meals would not obligate a repetition of birkat hamazon. Presumably, the same would be true of se`udah shelishit, since many opinions allow one to eat cake or even fruit for that meal.

An interesting question—which I did not see specifically raised, but seems worth discussion- is whether ya`aleh ve-yavo on Rosh haShanah would also be absolutely obligatory. The Shulhan Arukh notes that there were those who had the custom to fast on Rosh haShanah (because of the eimat hadin, the fear of Divine Judgement). While we do not rule that way—we rule that we eat and drink on Rosh haShanah as on any other holiday—there seems to be room to at least suggest that one would not repeat birkat hamazon if that part of the prayer was forgotten.

Yom Kippur is a related example, at least on occasions where a person is required to eat (for health reasons). The consensus of authorities is that such a person would say ya`aleh ve-yavo and retseh if Yom Kippur occurred on Shabbat. One who forgot these recitations, however, would not repeat the birkat hamazon, since it is not clear that ya`aleh ve-yavo is absolutely obligatory. Whereas on other holidays it is clearly obligatory to eat, here the question is whether circumstances forcing one to eat convert Yom Kippur into a regular holiday (so that the person should have a meal with bread), or whether it is nonetheless true that there is no obligation to eat a meal. As with most berakhot, when in doubt we do not repeat it to be certain that we have done it correctly.

Thus far, we have seen two extremes regarding obligations to eat. There is the obligation to eat a meal with bread on Shabbat and holidays (the question of what kinds of foods should be ingested at these meals—whether it has to be meat, chicken, fish, or whatever—is too complicated for this week’s discussion) and there is the simple obligation to avoid fasting for such days as Rosh Hodesh and Hanukkah. Between those two, kiddush be-makom se`udah, of eating food in the place where one makes kiddush, shows another kind of eating. Hazal wanted us to connect our mention of Shabbat or Yom Tov in kiddush to an act of eating a minimal meal, to give the kiddush even greater formality than just the cup of wine over which it is recited. For those purposes, cake (but not fruit or foods over which we recite shehakol) suffices. Some authorities even allowed drinking a whole cup of wine to qualify as the meal for kiddush be-makom se`udah purposes, although we only rely on this where absolutely necessary.

We thus have three different notions of required eating. To avoid prohibited fasting, a minimal amount of food or drink qualifies as breaking one’s fast. For purposes of establishing a se`udah in terms of kiddush, cake would suffice (although I remember seeing a teshuvah years ago by R. Moshe Sternbuch where he objected to having kiddush with less than a full meal). Finally, for Shabbat and Yom Tov, the obligation seems to be to eat a meal with bread .

One last meal distinction worth noting. According to most views, the de-oraita obligation to recite birkat hamazon only comes when a person is completely sated. The practice we have of reciting birkat hamazon even after eating only a kezayit is of Rabbinic provenance, and is seen in some sources as a particular source of merit for the Jewish people. This distinction within bread meals would bring to four the number of different types of eatings we have enumerated. Shabbat Shalom.