The first fruits signify that which first springs up, and afterwards grows as a child grows up to a man and hence they signify all which follows. Everything that follows is in the first, as the man is in the infant, and the tree in the young plant; and whereas this first exists before its successions, in like manner in heaven and in the church, therefore, the first fruits were holy unto the Lord, and the feast thereof was celebrated. The first fruits of the land, as in Exodus 23:19, signify the state of innocence which is in infancy.

(Referencat: Apocalypse Revealed 623)