Deuteronomy 16:9-11

9“Count off seven weeks from when you first begin to cut the grain at the time of harvest.

10Then celebrate the Festival of Harvest to honor the Lord your God. Bring him a voluntary offering in proportion to the blessings you have received from him.

11This is a time to celebrate before the Lord your God at the designated place of worship he will choose for his name to be honored. Celebrate with your sons and daughters, your male and female servants, the Levites from your towns, and the foreigners, orphans, and widows who live among you.