Numbers 28:26

26On the day of firstfruits, when you present an offering of new grain to the Lord during the Feast of Weeks,28:26 That is, Shavuot, the late spring feast of pilgrimage to Jerusalem; it is also known as the Feast of Harvest(see Exodus 23:16) or the Feast of Pentecost(see Acts 2:1). you are to hold a sacred assembly; you must not do any regular work.