According to the book of Leviticus the 23rd chapter, the Feast of First Fruits is observed on the 50th day after the beginning of our harvest and coincides with the ending of the Passover. It is because of the numbering of the 50 days that the Feast of First Fruits is also known as Pentecost or the Feast of Weeks.

It was during this time that the Israelites presented the First Fruits of their harvest to the priests of the Lord.

Numbers 18:12 (First Fruit = the best)

Numbers 18:12 All the best of the oil, and all the best of the wine, and of the wheat, the firstfruits of them which they shall offer unto the LORD, them have I given thee.  

Like many of the biblical feasts in the bible, the true understanding of their meaning is only fulfilled in our Lord Jesus Christ. It is through Christ that we begin to understand that this feast day was symbolic of his resurrection from the dead and the conversion of those who would believe on his name. 

1st Corinthians 15:20 But now is Christ risen from the dead, and become the firstfruits of them that slept. 

Just as the best of the fruits of the earth was presented to the priests of the Lord, so was Christ risen from the dead and presented perfect before the Heavenly Father. It is through the example and teaching of Jesus Christ that a man can repent, be converted from their sins and become the firstfruits or best of them that dwell on the earth.

James 1:18 Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures. 

Revelation 14:4 These are they which follow the Lamb whithersoever he goeth. These were redeemed from among men, being the firstfruits unto God and to the Lamb. 5 And in their mouth was found no guile: for they are without fault before the throne of God.  

In the book of Acts the 2nd chapter the Apostles of Christ received the gifts of the holy spirit and ministered to all those who travelled to Jerusalem to keep the Feast of Pentecost. Those who repented in the name of Christ became the true firstfruits unto God leaving us an example of faith.