The Lord had Moses tell them that in the future they were to set aside a tithe (1/10th) of their production each year and bring it, along with all their other voluntary offerings, to the place He would choose for them to worship Him. The Jews were about to enter the Promised Land.
Inviting the neighboring natives to join them, they held a three-day celebration patterned after their knowledge of the Feast of Tabernacles. When the Pilgrims had experienced their first successful harvest in the New World, they decided to give thanks for the Lord’s provision, even though half of them had died in the year since their arrival.
It was a celebration of the harvest, of God’s mercy in forgiving their sins for another year, and a remembrance of the time when He lived among them in the wilderness, setting them apart as His people. It was the crowning event in Israel’s cycle of fall feasts that also included Rosh Hashanah and Yom Kippur. Every year at Thanksgiving I’m reminded of the holiday’s origin, the Jewish Feast of Tabernacles.