Leviticus 23:37-40

37‘These are the feasts of the Lord which you shall proclaim to be holy convocations, to offer an offering made by fire to the Lord, a burnt offering and a grain offering, a sacrifice and drink offerings, everything on its day—

38besides the Sabbaths of the Lord, besides your gifts, besides all your vows, and besides all your freewill offerings which you give to the Lord.

39‘Also on the fifteenth day of the seventh month, when you have gathered in the fruit of the land, you shall keep the feast of the Lord for seven days; on the first day there shall be a sabbath-rest, and on the eighth day a sabbath-rest.

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