Leviticus 23:37-40

37"These are the appointed feasts of the Lord, which you shall proclaim as times of holy convocation, for presenting to the Lord food offerings, burnt offerings and grain offerings, sacrifices and drink offerings, each on its proper day,

38besides the Lord's Sabbaths and besides your gifts and besides all your vow offerings and besides all your freewill offerings, which you give to the Lord.

39"On the fifteenth day of the seventh month, when you have gathered in the produce of the land, you shall celebrate the feast of the Lord seven days. On the first day shall be a solemn rest, and on the eighth day shall be a solemn rest.

40And you shall take on the first day the fruit of splendid trees, branches of palm trees and boughs of leafy trees and willows of the brook, and you shall rejoice before the Lord your God seven days.