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.