Deuteronomy 16:9-12

“You shall count seven weeks. Begin to count the seven weeks from the time the sickle is first put to the standing grain. Then you shall keep the Feast of Weeks to the LORD your God with the tribute of a freewill offering from your hand, which you shall give as the LORD your God blesses you. And you shall rejoice before the LORD your God, you and your son and your daughter, your male servant and your female servant, the Levite who is within your towns, the sojourner, the fatherless, and the widow who are among you, at the place that the LORD your God will choose, to make his name dwell there. You shall remember that you were a slave in Egypt; and you shall be careful to observe these statutes.