Leviticus 23:40-43

40On the first day you are to take branches from luxuriant trees—from palms, willows and other leafy trees—and rejoice before the Lord your God for seven days. 41Celebrate this as a festival to the Lord for seven days each year. This is to be a lasting ordinance for the generations to come; celebrate it in the seventh month. 42Live in temporary shelters for seven days: All native-born Israelites are to live in such shelters 43so your descendants will know that I had the Israelites live in temporary shelters when I brought them out of Egypt. I am the Lord your God.’ ”