Leviticus 23:10-12

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,

11and 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.

12On the day you wave the sheaf you must also offer a flawless yearling lamb for a burnt offering to the Lord,