Deuteronomy 16:8-10 New American Bible (Revised Edition) (NABRE)
8 For six days you shall eat unleavened bread, and on the seventh day there shall be a solemn assembly for the Lord, your God; on that day you shall do no work.
Feast of Weeks. 9 You shall count off seven weeks; begin to count the seven weeks from the day when the sickle is first put to the standing grain. 10 You shall then keep the feast of Weeks[a] for the Lord, your God, and the measure of your own voluntary offering which you will give shall be in proportion to the blessing the Lord, your God, has given you.