The Feast of Weeks is a period of giving thanks to God with the fruits of the harvest for seven weeks after the Feast of Firstfruits, which is the day after the first Sabbath, following the seven-day observance of the Feast of Unleavened Bread, which is the day after the Passover.
Deuteronomy 16:9You shall count seven weeks for yourself; begin to count the seven weeks from the time you begin to put the sickle to the grain.Deuteronomy 16:10Then 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;Deuteronomy 16:11and you shall rejoice before the Lord your God, you and your son and your daughter, your male and female servants, the Levite who is within your gates, the stranger and the fatherless and the widow who are among you, at the place where the Lord your God chooses to make His name abide.Deuteronomy 16:12And you shall remember that you were a slave in Egypt, and you shall be careful to observe these statutes.
Leviticus 23:15And you shall count for yourselves from the day after the Sabbath, from the day that you brought the sheaf of the wave offering: seven Sabbaths shall be completed.