Leviticus 23:27, 32

“Be careful to celebrate the Day of Atonement on the tenth day of that same month—nine days after the Festival of Trumpets. You must observe it as an official day for holy assembly, a day to deny yourselves and present special gifts to the LORD.

This will be a Sabbath day of complete rest for you, and on that day you must deny yourselves. This day of rest will begin at sundown on the ninth day of the month and extend until sundown on the tenth day.”