Leviticus 23:40-41

⁴⁰and ye have taken to yourselves on the first day the fruit of beautiful trees, branches of palms, and boughs of thick trees, and willows of a brook, and have rejoiced before Jehovah your God seven days.

⁴¹'And ye have kept it a feast to Jehovah, seven days in a year — a statute age-during to your generations; in the seventh month ye keep it a feast.