There is an ancient Jewish belief that there are seven imaginary, mystical guests, called Ushpizin in Aramaic, who visit families on Sukkot, the Festival of Tabernacles that commemorates the protection afforded by the Eternal as the Israelites wandered the desert. The guests, one for each day of the holiday, are said to be the biblical figures Abraham, Isaac, Jacob, Moses, Aaron, Joseph, and David. Each is invited in turn, with a prayer formulated by 16th-century Kabbalists, to join the family in the sukkah, the temporary shelter built of natural materials that is at the heart of the holiday.