Leviticus 23:39-41

39“Remember that this seven-day festival to the Lord—the Festival of Shelters—begins on the fifteenth day of the appointed month, after you have harvested all the produce of the land. The first day and the eighth day of the festival will be days of complete rest.

40On the first day gather branches from magnificent trees—palm fronds, boughs from leafy trees, and willows that grow by the streams. Then celebrate with joy before the Lord your God for seven days.

41You must observe this festival to the Lord for seven days every year. This is a permanent law for you, and it must be observed in the appointed month from generation to generation.