I. The Eighth Day
"You shall rejoice in your festival... you shall be only (ach) joyous" (Devarim 16:14,15). Rashi cites the Gemara (Sukkah 48a) that the second command adds that the mitzva of simcha applies to the night of Shmini Atzeres as well. What about the day of Shmini Atzeres? Rashi (48a) explains that one must offer shelamim on the seventh day in order to eat its meat on the eighth night, so certainly (kal vachomer) he must eat the meat the eighth day, since the main (ikar) simcha is during the day.
However, in Pesachim (71a) Rashi states that the mitzva of simcha is limited to the eating of the shelamim meat, applies only to the eighth night, and the eighth day is excluded from this mitzva, as the Torah says twice (Vayikra 23:40, Devarim 16:15) regarding simcha, "seven days". How can this contradiction in Rashi be resolved? This question was raised by the Maharsha (Sukkah 42b).
Rav Bezalel Zolty (Mishnas Ya'avetz, Orach Chaim 41:2) resolves the seeming contradiction answers based on a dispute regarding shelamim which were slaughtered on erev yom tov (Pesachim 70b-71a). Ulla holds that one does not fulfill the mitzva, because the slaughtering must take place at the time of simcha (zevicha b'shas simcha), i.e. on yom tov itself. Ravin disagrees and maintains that one does fulfill the mitzva because we do not require slaughtering at the time of simcha.
Rav Zolty explains that Rashi in Pesachim is explaining the position of Ulla. The night of Shmini Atzeres is part of the seven days of Sukkos because when it comes to kodshim, a halachic day begins in the morning and continues through the subsequent night (Chulin 83a). As such, the mitzva of simcha begins on the morning of the first day of Sukkos and extends through the night (only) of the eight day, for a total of seven halachic kodshim days. (It cannot be fulfilled on the first night since, from the perspective of how we count days for purposes of kodshim, Sukkos has not begun yet, nor does it extend to daytime of the eighth day, which is past the seven [kodshim] days that the Torah specified twice. Although the Mishna (Sukkah 48a) states that simcha is observed for eight days, it means that it applies on eight calendar days, from the dawn of the fifteenth of Tishrei until the dawn of the twenty-second.)
Rashi in Sukkos, however, is explaining the position of Ravin. According to Ravin, the eighth night is not an extension of the seven days of Sukkos, rather it is part of the independent mitzva of Shmini Atzeres. Rav Zolty says that the halacha follows Ravin (see Rambam Hilchos Chagiga 2:12 and Hilchos Yom Tov 6:17), and a proof to this is that the Gemara (48a) must have adopted the position of Ravin since it suggests that the word "Ach" comes to include the first night. This presumes, as Rashi explains, Ravin's position that the shelamim can be slaughtered on erev yom tov and eaten on the first night.
II. Night and/or Day
The Chazon Ish (Orach Chaim 124, 71a) is unsure whether one must eat shelamim meat day and night, or is only once, either during the day or night, enough. The Mishna (Sukkah 42b) states: "Lulav and arava six and seven, Hallel and simcha eight." Six and seven depend on whether the first or last day of Sukkos is on Shabbos, as the Mishna explains. Tosfos (ibid.) asks: simcha is also not always eight days; if the eighth day is motzaei Shabbos, the mitzva is only seven days, since shelamim may not be slaughtered on Shabbos, and if slaughtered on Friday, it may not be eaten beyond the day of Shabbos. The Maharshal asks: given that every Sukkos has a motzaei Shabbos, why did Tosfos ask his question only regarding the eighth night falling out on motzaei Shabbos? Maharshal answers that Tosfos chose the eighth night because it is included (48a) explicitly, but in reality the question applies every year. The Maharsha disagrees, saying that in other years the mitzva can be fulfilled on Sunday during the day, and only when the eighth night is on motzaei Shabbos is there a question, since Tosfos agrees with Rashi in Pesachim that the mitzva does not extend until the eighth day. The Maharsha clearly holds that it is sufficient to eat meat by day, on Sunday in most years. The Chazon Ish's doubt is thus resolved leniently (according to the Maharshal the doubt remains.)
One question remains: How do we divide the days? Does the night follow the day as in kodshim, or does the night precede the day as in all other areas of halacha? Perhaps this, too, depends on the dispute between Ulla and Ravin. According to Ulla, the obligation of simcha is in place for seven twenty four hour days, from dawn of the fifteenth until dawn of the twenty-second, and the days begin and end at dawn, as in kodshim. However, according to Ravin, the obligation of simcha is eight full days, from sunset preceding the fifteenth until sunset of the twenty-second. If so, the day is divided from sunset to sunset, as in all other halachos. As mentioned, the halacha is according to Ravin.
III. Nowadays
The Rambam (Hilchos Yom Tov 6:17) includes other types of simcha, such as meat and wine, in the biblical mitzva of simcha. Tosfos (Moed Kattan 14b) writes that only shelamim meat is a biblical mitzva, and nowadays simcha is only rabbinic.
Tosfos (Sukkah 42b) answers the question about motzaei Shabbos, when there is no shelamim meat, by citing the Gemara (Pesachim 71a) where Ulla is questioned: when the first day of Sukkos is Shabbos, how does one fulfill simcha? One may not slaughter on Shabbos, and Friday is not bizman simcha. Rav Papa answers: one fulfills the mitzva with clothing and wine. Presumably, this means clothing for women and wine for men (Pesachim 109a). The Rambam adds meat, together with wine.
Tosfos here contradicts the Tosfos in Moed Kattan 14b and maintains that all types of simcha are a biblical mitzva. This contradiction can be answered in the same manner in which Rav Zolty answered the one above. The proof that clothes and wine are a biblical mitzva is only according to Ulla and R. Papa, but the halacha follows Ravin. When the first day of Sukkos is on Shabbos, the mitzva is fulfilled with shelamim meat slaughtered on Friday, and there is no need to say that other forms of simcha are a biblical mitzva. Therefore, l'halacha, Tosfos (Moed Kattan) rules that it is only rabbinic.
The Piskei Teshuvos (530 fn. 63, fn. 73 in 2021 edition) rules that one must eat meat and drink wine twice daily on chol hamoed. According to our analysis, once a day, from sunset to sunset, suffices, and this is the opinion of Rav Moshe Feinstein and Rav Y.S. Elyashiv as well (cited there). The Piskei Teshuvos (529 fn 99) rules that one should eat red meat, as opposed to chicken. According to the Rambam this is an obligation, while according to the Shulchan Aruch it is a mitzva but not an obligation (Biur Halacha 529:2). If one does not enjoy meat or wine, he should fulfill the mitzva with what he enjoys. Even on Yom Tov itself, eating meat once a day is sufficient. In our home, on Shabbos we eat chicken, on yom tov we eat red meat once each day. On the second night of Shavuos, and the night of Simchas Torah, we eat dairy.
May we soon merit the rebuilt Beis Hamikdash and eating the meat of shelamim and fulfilling the biblical mitzva of simchas yom tov according to all opinions.
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