Leviticus 23:41-45

And 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.

Ye shall dwell in booths seven days; all that are Israelites born shall dwell in booths:

That 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.

And Moses declared unto the children of Israel the feasts of the LORD.