Leviticus 23:24, 39

“Give the following instructions to the people of Israel. On the first day of the appointed month in early autumn, you are to observe a day of complete rest. It will be an official day for holy assembly, a day commemorated with loud blasts of a trumpet.

“Remember that this seven-day festival to the LORD—the Festival of Shelters—begins on the fifteenth day of the appointed month, after you have harvested all the produce of the land. The first day and the eighth day of the festival will be days of complete rest.