Deuteronomy 31:10-12
And Moses commanded them, saying, At the end of every seven years, in the solemnity of the year of release, in the feast of tabernacles,
Nave's Topical Index—AKJV

Nehemiah 8:18
Also day by day, from the first day to the last day, he read in the book of the law of God. And they kept the feast seven days; and on the eighth day was a solemn assembly, according to the manner.
Nave's Topical Index—AKJV