The Feast of Pentecost: Called The: Feast of Weeks
Source: TTT
Exodus 34:22
And you are to celebrate the Feast of Weeks with the firstfruits of the wheat harvest, and the Feast of Ingathering at the turn of the year.
Deuteronomy 16:10
And you shall celebrate the Feast of Weeks to the LORD your God with a freewill offering that you give in proportion to how the LORD your God has blessed you,