The Feast of Tabernacles is prescribed in Leviticus 23 and Deuteronomy 16.
The festival is a week long feast that begins Sundoown on the 14th Day of the 7th Month of the year, the Hebrew month Tishrei, roughly late-September to mid-October on our modern calendar.
All of Israel would camp out in tents for the entire week (Lev 23:42),
"Ye shall dwell in booths seven days; all that are Israelites born shall dwell in booths:" Lev 23:42
offering all types of sacrifices as burnt offerings to the LORD (Lev 23:37-38).
These are the feasts of the Lord, which ye shall proclaim to be holy convocations, to offer an offering made by fire unto the Lord, a burnt offering, and a meat offering, a sacrifice, and drink offerings, every thing upon his day:
Beside the sabbaths of the Lord, and beside your gifts, and beside all your vows, and beside all your freewill offerings, which ye give unto the Lord.
Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast unto the Lord seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath. Lev 23:37-38
The prescription in Deuteronomy extends participation in the festival not only to (male) Israelite citizens but also to priests, orphans, widows, immigrants, and both male and female children and slaves (Deut 16:14).
"And thou shalt rejoice in thy feast, thou, and thy son, and thy daughter, and thy manservant, and thy maidservant, and the Levite, the stranger, and the fatherless, and the widow, that are within thy gates." Deut 16:14
The purpose of the Feast of Booths was to remember the time that the children of Israel were wandering in the wilderness after God had freed them from the captivity of Egypt.
It is also to remember the giving of the Law and to renew the covenant made between Israel and the LORD (Duet 31:10-13).
"And Moses commanded them, saying, At the end of every seven years, in the solemnity of the year of release, in the feast of tabernacles,
When all Israel is come to appear before the Lord thy God in the place which he shall choose, thou shalt read this law before all Israel in their hearing.
Gather the people together, men and women, and children, and thy stranger that is within thy gates, that they may hear, and that they may learn, and fear the Lord your God, and observe to do all the words of this law:
And that their children, which have not known any thing, may hear, and learn to fear the Lord your God, as long as ye live in the land whither ye go over Jordan to possess it." Deut 31:10-13
The Feast of Booths lasted seven days. On the eighth day, a separate but related holiday was celebrated, the Day of Assembly (Azaret). On this day, the people were to “have a holy convocation” (Lev 23:36, NASB), perhaps better rendered “a convocation of holiness,” i.e. a “declaration of holiness” or “call to holiness.” The eighth day was to be a day of rest (Num 29:35) where the people would solemnly dedicate themselves to the LORD (Neh 8:18). In Chronicles, this is the day on which the altar was to be dedicated (2 Chr 7:9). Ezekiel may have this day in mind when he says it will be the day that the LORD accepts the restoration of offerings in the eschatological temple (Ezek 43:27)
