Leviticus 23:36

23:36 For seven days you must present a gift to the Lord. On the eighth day there is to be a holy assembly for you, and you must present a gift to the Lord. It is a solemn assembly day; you must not do any regular work.

Nehemiah 8:18

8:18 Ezra read in the book of the law of God day by day, from the first day to the last. They observed the festival for seven days, and on the eighth day they held an assembly as was required.