The Feast of Firstfruits is one of the most important days in the overall Plan of God. God gave His Truth to Israel and established the Old Testament Church on the day of Pentecost while in the process of leading them (in that first year of the Exodus) out of the land of Egypt. And on the first Pentecost after Christ’s death, burial, and resurrection from the dead, after having been accepted by the Father as the First of the Firstfruits, God sent His Spirit as a help to those He would call in this lifetime, upon repentance of their past sins, baptism, and the laying on of hands by His ordained Ministry.
If those called of God are successful in their calling, remaining true to God and His established Way of life, they will be among those referred to as the Firstfruits of the Lord, Jesus Christ being the First of the Firstfruits.
The day of Pentecost pictures these Firstfruits of the Lord. Pentecost can be viewed as their day!