Leviticus 23:23-27

23The LORD also said to Moses, 24“Speak to the Israelites and say, ‘On the first day of the seventh month you are to have a day of rest, a sacred assembly announced by trumpet blasts.1 25You must not do any regular work, but you are to present a food offering to the LORD.’”

26Again the LORD said to Moses, 27“The tenth day of this seventh month is the Day of Atonement. You shall hold a sacred assembly and humble yourselves,2 and present a food offering to the LORD.