The Feast of Tabernacles
The Feast of Tabernacles is a week-long autumn harvest festival. Tabernacles is also known as the Feast of the Ingathering, Feast of the Booths, Sukkoth, Succoth, or Sukkot (variations in spellings occur because these words are transliterations of the Hebrew word pronounced "Sue-coat"). The two days following the festival are separate holidays, Shemini Atzeret and Simkhat Torah, but are commonly thought of as part of the Feast of Tabernacles.
The Feast of Tabernacles was the final and most important holiday of the year. The importance of this festival is indicated by the statement, "This is to be a lasting ordinance." The divine pronouncement, "I am the Lord your God," concludes this section on the holidays of the seventh month. The Feast of Tabernacles begins five days after Yom Kippur on the fifteenth of Tishri (September or October). It is a drastic change from one of the most solemn holidays in our year to one of the most joyous. The word Sukkoth means "booths," and refers to the temporary dwellings that Jews are commanded to live in during this holiday, just as the Jews did in the wilderness. The Feast of Tabernacles lasts for seven days and ends on the twenty-first day (3x7) of the Hebrew month of Tishri, which is Israel's seventh month.
This holiday has a dual significance: historical and agricultural (just as Passover and Pentecost). Historically, it was to be kept in remembrance of the dwelling in tents in the wilderness for the forty-year period during which the children of Israel were wandering in the desert.
It is expounded in Leviticus 23:43 That your generations may know that I made the children of Israel to dwell in booths, when I brought them out of the land of Egypt: I am the LORD your God.
What were they to remember?
Matthew Henry's commentary explains,
1.) The meanness of their beginning, and the low and desolate state out of which God advanced that people. Note: Those that are comfortably fixed ought often to call to mind their former unsettled state, when they were but little in their own eyes. 2.) The mercy of God to them, that, when they dwelt in tabernacles, God not only set up a tabernacle for Himself among them, but, with the utmost care and tenderness imaginable, hung a canopy over them, even the cloud that sheltered them from the heat of the sun. God's former mercies to us and our fathers ought to be kept in everlasting remembrance. The eighth day was the great day of this holiday, because then they returned to their own houses again, and remembered how, after they had long dwelt in tents in the wilderness, at length they came to a happy settlement in the land of promise, where they dwelt in goodly houses.
And they would the more sensibly value and be thankful for the comforts and conveniences of their houses when they had been seven days dwelling in booths. It is good for those that have ease and plenty sometimes to learn what it is to endure hardness.
They were to keep this holiday in thankfulness to God for all the increase of the year; however, the emphasis is that Israel's life rested upon redemption which in its ultimate meaning is the forgiveness of sin. This fact separates this holiday from the harvest festivals of the neighboring nations whose roots lay in the mythological activity of the gods.
Was the first Thanksgiving a Feast of Tabernacles Celebration?
Many Americans, upon seeing a decorated sukkah for the first time, remark on how much the sukkah (and the holiday generally) reminds them of Thanksgiving. The American pilgrims, who originated the Thanksgiving holiday, were deeply religious people. As they were trying to find a way to express their thanks for their survival and for the harvest, it is quite possible that they looked to the Bible (Leviticus 23:39) for an appropriate way of celebrating and based their holiday in part on the Feast of Tabernacles.
Note: celebrating Thanksgiving on the third Thursday of November was established by the American government and may not necessarily coincide with the pilgrim's first observance.http://biblicalholidays.com/tabernacles.htm