What Are Firstfruits? Introduction and Commandments

"Firstfruits" are something that the bible mentions several times, and, especially in the New Testament, it seems like a really important concept to understand:

1. Christ is the firstfruits of those who have died (1 Corinthians 15:20)
2. God's church "[has] the firstfruits of the Spirit" (Romans 8:23)
3. God's church is called to be the "firstfruits of His creatures" (James 1:18)
4. The 144,000 of Revelation 14 are "redeemed from among men, being firstfruits to God and to the Lamb" (Revelation 14:4)

What exactly are firstfruits? Why were the New Testament writers making comparisons using this idea? What did they mean by these statements? These are questions that I hope to thoroughly answer in a series of articles between now and Pentecost! In this article, we'll start with an introductory analysis of what firstfruits are and what God commanded to be done with them.