Who are these “spirits in prison” and what did Christ preach to them?
For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit: By which also he went and preached unto the spirits in prison; (1 Pet. 3:18-19 KJV)
And so it is written, “The first man Adam became a living being.” The last Adam became a life-giving spirit. (1 Cor. 15:45 NKJ)
Upon physical death the human spirit of God the Eternal Son was “quickened” by the Holy Spirit and became a “life giving spirit” (John 6:63). By that same Spirit Jesus’ human spirit descended into Hell (Eph. 4;9) and preached to the spirits in prison.
Christ’s preaching to spirits in prison took place between the crucifixion and His ascension. Those he preached to “disbelieved” (544 ἀπειθέω apeitheo). From Jude 1:5-6 associating what the “sons of God” did in Genesis 6:4 to giving themselves over to “strange flesh” and the law’s prohibition against mixing “breeds with another kind” (Lev. 19:19) we can deduce the hybrid children of the “sons of God” (Gen. 6:4) couldn’t believe God could forgive their “strange flesh”.
That Christ preached the gospel and they repented and believed is clearly required by the context, their response to the Gospel “the pledge of a good conscience” is a “corresponding like figure” to the church’s belief in the Gospel and subsequent salvation:
20 They refused to believe long ago, while God patiently waited to receive them, in Noah’s time when the ark was being built. In it only a few, that is eight souls, were saved through water.
21 It is the baptism corresponding to this water which saves you now — not the washing off of physical dirt but the pledge of a good conscience given to God through the resurrection of Jesus Christ,
22 who has entered heaven and is at God’s right hand, with angels, ruling forces and powers subject to him. (1 Pet. 3:20-4:1 NJB)
Nephilim Fallen Angels and the Sons of God
Angels are cast out of Heaven Twice?
As in the days of Noe, so shall it be also in the days of the Son of man
Are the Ministering Spirits in Hebrew 1:14 spirits or angels?