On the day of Pentecost, AD 31, God sent His Spirit to begin His church - to beget and strengthen the firstfruits He was beginning to call into His church, symbolically represented by one of the "wave loaves." The New Testament festival of Pentecost is now a memorial commemorating the founding of the New Testament church of God through the receiving of the Holy Spirit.
God's church observes the Feast of Firstfruits as an annual reminder of this step in God's Master Plan: God's people today are merely the firstfruits - the small first group to be offered salvation through Christ. The world, except for the few called, is cut off from God - not yet called to salvation - neither saved nor lost - not yet judged. But the members of God's church are being judged (I Peter 4:17) - judged in how well they are preparing for God's Kingdom!
The day of Pentecost pictures the church being called and trained for the special mission of preparing for the time when God will open salvation to the world, when they will be kings and teachers, co-rulers and co-saviors with and under Christ, their Husband!