Booths - According to Jewish tradition, what were used at the Feast of Tabernacles were strictly “tabernacula,” structures of boards, with a covering of boughs.
The “booth” in which the Israelite kept the Feast, and the “tent” which was his ordinary abode in the wilderness, had this in common - they were temporary places of sojourn, they belonged to camp-life. The seven days of abode in the booths of the festival was thus a fair symbol of the forty years of abode in tents in the wilderness. The Feast might well become the appointed memorial of this period of their history for the ages to come.
All that are Israelites born - The omission of the foreigners in this command is remarkable. Perhaps the intention was that on this joyous occasion they were to be hospitably entertained as guests. Compare Deuteronomy 16:14.