Deuteronomy 16:8-10

New Revised Standard Version, Anglicised Catholic Edition

⁸ For six days you shall continue to eat unleavened bread, and on the seventh day there shall be a solemn assembly for the Lord your God, when you shall do no work.

The Festival of Weeks Reviewed

⁹ You shall count seven weeks; begin to count the seven weeks from the time the sickle is first put to the standing grain. ¹⁰ Then you shall keep the festival of weeks to the Lord your God, contributing a freewill-offering in proportion to the blessing that you have received from the Lord your God.