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:
An offering of “first fruits,” that is, from the beginning of the harvest, is commanded. If you remember well, the law commands this is to be done on the day of Pentecost. This was obviously given to them as a “shadow,” but the truth was reserved for us. For on the day of Pentecost, after they offered up the sacrifice of prayers, the church of the apostles received the first fruits of the coming of the Holy Spirit.
[AD 253] Origen of Alexandria on Deuteronomy 16:10