Leviticus 23:39-43
39Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast unto the LORD seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath.
40And ye shall take you on the first day the boughs of goodly trees, branches of palm trees, and the boughs of thick trees, and willows of the brook; and ye shall rejoice before the LORD your God seven days.
41And ye shall keep it a feast unto the LORD seven days in the year. It shall be a statute for ever in your generations: ye shall celebrate it in the seventh month.
42Ye shall dwell in booths seven days; all that are Israelites born shall dwell in booths:
43That your generations may know that I made the children of Israel to dwell in booths, when I brought them out of the land of Egypt: I am the LORD your God.
(KJV)