Shemini Atzeret and Simchat Torah שמיני עצרת ושמחת תורה
The eighth day after Sukkot—a festival in its own right; on it the yearly cycle of Torah reading is finished and at once begun again.
The Torah names it briefly: "on the eighth day you shall have a solemn assembly." The sages read that brevity as the explanation: the seven days of Sukkot brought seventy bulls for the seventy nations, and on the eighth a single one—"your parting is hard for Me, stay one day more." Hence the name: atzeret, "a holding back."
From this day one stops speaking of rain "in its season" and begins to ask for it outright; in the Land of Israel a little later, seven weeks after the festival, so that pilgrims may reach home.
Simchat Torah is a custom, not a commandment of the Torah: the yearly cycle is finished with the last words of Deuteronomy and, without pausing, the opening of Genesis is read, so that there is no emptiness between the end and the beginning. In the Land of Israel this is the same eighth day; in the diaspora, the ninth. The custom of dancing with the scrolls took shape in the time of the Geonim and spread quickly.
On the timeline
Sources
Tanakh
- Leviticus 23:36 — «on the eighth day a solemn assembly»
- Numbers 29:35 — the single bull of the eighth day
Chazal: Mishnah, Talmud, midrash, Zohar
- Sukkah 55b — seventy bulls for the seventy nations
- Megillah 31a — reading the last portion of the Torah on this day
Rishonim
- Rashi on Leviticus 23:36 — «your parting is hard for Me»
Basis: Talmud and midrash.