Deuteronomy 16:10
And thou shalt keep the feast of weeks unto the LORD thy God with a tribute of a freewill offering of thine hand, which thou shalt give unto the Lord thy God, according as the LORD thy God hath blessed thee: And thou shalt keep the feast of weeks unto the LORD thy God with a tribute of a freewill offering of thine hand, which thou shalt give unto the Lord thy God, according as the LORD thy God hath blessed thee:
The Feast of Weeks is Pentecost, kept seven weeks after the Passover as a day of divine appointment and a one-day religious observance. It required going to the temple to gather before God, setting aside unnecessary work. There the people were to present the first-fruits of all the harvest.
Two loaves baked with leaven were presented before God as an expression of gratitude for the grain He had prepared for food. They were also to bring a tribute of a freewill, voluntary offering, giving in proportion to how God had blessed them, and were not to come empty-handed. The feast joined harvest joy with remembering God's mercies and blessings, with praise, thanksgiving, and rejoicing.
The rejoicing was to include servants, strangers, orphans, and widows, welcoming the stranger to share in the celebration and its blessings. The gifts brought showed how highly the people valued God's blessings and revealed whether gratitude or selfishness ruled their hearts, whether they loved the Giver or were selfishly attached to the gifts. Presenting first-fruits acknowledged dependence on God as the great Giver of all good and the obligation to return to God from what He had entrusted to them to sustain His cause.
On that feast day God poured out His Spirit on the little company of believers as the first-fruits of the Christian church.