1 Corinthians 15:20-23 presents Jesus as the firstfruits of those who have fallen asleep. What is the significance of 'firstfruits?' Is this related to instructions in the Hebrew Bible about firstfruits (e.g. Exodus 23:14-18, Exodus 34:22-26, Leviticus 2:12-14, Leviticus 23:9-21, Numbers 28:26, Deuteronomy 26:1-11)?
First, as touching the passages from the Hebrew Bible such as those from Exodus, Leviticus, Numbers, and Deuteronomy; we must first address two significant facts.
One key to understanding is found in the words, "...each in his own order..."
Messiah was (and remains) the best of humanity, and he was offered to God by, and on behalf of sinful humanity. Messiah being the one who did the "work" of salvation is naturally the first to partake in the resurrection of the righteous dead. After that, and each in his own order, the resurrection will occur for others, both righteous and unrighteous.
The apostle Paul had a marvelous insight into this when he stated:
Paul's emphasis on “together” in these verse 22 does not include believers in Messiah, who are specifically mentioned in verse 23, but rather points to the various parts of the natural Creation.
Paul began this section in verse 18 by referring to the believers’ “present sufferings," a subject to which he now returned to in verse 23.
Believers are described as the ones having the firstfruits of the Spirit. This is a declaration that the Holy Spirit is “the firstfruits” (aparchēn) of God’s work of salvation and re-creation in believers. Believers "spirits" have been resurrected from the dead and we are now spiritually alive in the Messiah. Believers are therefore awaiting the ultimate fulfillment of their sanctification, i.e., the redemption of their mortal (death doomed) physical bodies.
Yeshua Messiah has already received his glorified body and, as such, is the firstfruits of those who believe on him. And now believers groan together with all of creation in hope of receiving our immortal bodies and becoming fully conformed to the image of Messiah (Romans 8:29).