Leviticus 23:39-44

“So, summing up: On the fifteenth day of the seventh month, after you have brought your crops in from your fields, celebrate the Feast of GOD for seven days. The first day is a complete rest and the eighth day is a complete rest. On the first day, pick the best fruit from the best trees; take fronds of palm trees and branches of leafy trees and from willows by the brook and celebrate in the presence of your GOD for seven days—yes, for seven full days celebrate it as a festival to GOD. Every year from now on, celebrate it in the seventh month. Live in booths for seven days—every son and daughter of Israel is to move into booths so that your descendants will know that I made the People of Israel live in booths when I brought them out of the land of Egypt. I am GOD, your God.” Moses posted the calendar for the annual appointed feasts of GOD which Israel was to celebrate.