Leviticus 23:10-11

23:10 “Speak to the Israelites and tell them, ‘When you enter the land that I am about to give to you and you gather in its harvest, then you must bring the sheaf of the first portion of your harvest to the priest, 23:11 and he must wave the sheaf before the Lord to be accepted for your benefit – on the day after the Sabbath the priest is to wave it.

Leviticus 25:8

Regulations for the Jubilee Year of Release

25:8 “‘You must count off seven weeks of years, seven times seven years, and the days of the seven weeks of years will amount to forty-nine years.

Exodus 34:22

34:22 “You must observe the Feast of Weeks – the firstfruits of the harvest of wheat – and the Feast of Ingathering at the end of the year.

Deuteronomy 16:9-10

The Festival of Weeks

16:9 You must count seven weeks; you must begin to count them from the time you begin to harvest the standing grain. 16:10 Then you are to celebrate the Festival of Weeks before the Lord your God with the voluntary offering that you will bring, in proportion to how he has blessed you.