Deuteronomy 16:9-12

9“You shall count seven weeks for yourself; you shall begin to count seven weeks from the time you first put the sickle to the standing grain.

10Then you shall celebrate the Feast of Weeks to the Lord your God with a tribute of a freewill offering from your hand, which you shall give [to Him] just as the Lord your God blesses you;

11and you shall rejoice before the Lord your God, you and your son and your daughter and your male and female servants and the Levite who is within your [city] gates, and the stranger and the orphan and the widow who are among you, at the place where the Lord your God chooses to establish His Name (Presence).

12You shall remember that you were a slave in Egypt, and you shall be careful to obey these statutes.