Leviticus 23:34-36

34 “Say to the Israelites: ‘On the fifteenth day of the seventh month the LORD’s Festival of Tabernacles begins, and it lasts for seven days.
35 The first day is a sacred assembly; do no regular work.
36 For seven days present food offerings to the LORD, and on the eighth day hold a sacred assembly and present a food offering to the LORD. It is the closing special assembly; do no regular work.