There is a positive mitzva to experience simḥa (joy) on the festivals, as it is written: “You shall rejoice in your festival (ve-samaḥta be-ḥagekha)” (Devarim 16:14). We have already seen that Shabbat and Yom Tov are “mikra’ei kodesh” and that it is a mitzva to sanctify them with festive meals and fancy clothing (Sifra, Emor 12:4). The mitzva of simḥa on Yom Tov adds another layer: having more meat and wine at Yom Tov meals than at Shabbat meals (as explained in the next paragaph). Similarly, there is a mitzva to have fancier clothing for Yom Tov than for Shabbat. On Shabbat it is enough to wear respectable clothing, whereas on Yom Tov there is a mitzva to wear the nicest clothes. If one must buy festive clothes, it is proper to buy them before a festival (SA 529:1; MA ad loc. 4; MB ad loc. 12).
There are four components to the mitzva of simḥa. First, the primary expression of the mitzva is to do something especially enjoyable, which causes one’s joy to permeate the entire festival. Given the differences between men and women, to bring men joy, festive meals with meat and wine should be held (as explained in the next section), and to bring women joy, new clothing or jewelry should be purchased for her before the festival. One item of clothing is enough to fulfill this mitzva (see section 10 below). To make children happy, candy should be bought for them, as this is what makes them happiest.
Second, as described above, the term “mikra’ei kodesh” is applied to the holidays as well as Shabbat, and translates into a mitzva to sanctify them with festive meals and nice clothes. Since Yom Tov has an additional mitzva of simḥa, it is incumbent on both men and women to make sure that their Yom Tov meals and clothes are nicer than those of Shabbat. There is also a mitzva to study Torah on Yom Tov, because it is enjoyable (as explained above in section 5).
Third, it is a mitzva to participate in whatever activities one generally enjoys – like singing, dancing, and going on outings (section 13 below).
Fourth, throughout Yom Tov it is a mitzva to be in a good mood and to avoid things that cause anguish. It is therefore forbidden to mourn, eulogize, or fast (section 14 below).
One must enjoy the festival and not rejoice in something that is liable to make him forget about the joy of the festival. For this reason, one may not get married on Ḥol Ha-mo’ed. “‘You shall rejoice in your festival’ and not in your wife” (MK 8b). One who gets married is so happy with his wife that he does not pay attention to the simḥa of the festival. However, one may get married right before Yom Tov and hold Sheva Berakhot at the Yom Tov meals because, in this case, the simḥa of the festival is primary, and the simḥa of the Sheva Berakhot does not detract from it but rather reinforces it (SA 546:1-3; 10:4 below).
Even though the mitzva of simḥa is explicitly mentioned in the context of the pilgrimage festivals, Rosh Ha-shana is included in this mitzva as well, because all biblical holidays are equated with one another. Nevertheless, the simḥa of the pilgrimage festivals is greater, as there is a mitzva then to make a pilgrimage to the Temple and to offer shalmei simḥa (festive peace offerings, explained below) (MB 597:1).