Deuteronomy 16:9-12

⁹"You shall count seven weeks; begin to count the seven weeks from the time you first put the sickle to the standing grain. ¹⁰Then 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; ¹¹and you shall rejoice before the LORD your God, you and your son and your daughter, your manservant and your maidservant, the Levite who is within your towns, the sojourner, the fatherless, and the widow who are among you, at the place which the LORD your God will choose, to make his name dwell there. ¹²You shall remember that you were a slave in Egypt; and you shall be careful to observe these statutes.