The “spirits in prison” are mentioned in the broader context of suffering righteously. First Peter 3:18–20 says, “For Christ also died for sins once for all, the just for the unjust, so that He might bring us to God, having been put to death in the flesh, but made alive in the spirit; in which also He went and made proclamation to the spirits now in prison, who once were disobedient, when the patience of God kept waiting in the days of Noah, during the construction of the ark” (NASB95). Some people use this passage to infer what Jesus did during the time that His body was in the grave. As background, please read our article on “Where was Jesus for the three days between His death and resurrection?”
We know three things for sure about the spirits mentioned in 1 Peter 3:19. They are incorporeal, they are imprisoned, and their sin was committed before the Flood. Their relation to Jesus and the nature of His announcement to them are open to speculation. Who exactly these spirits are has been the subject of some debate through the years. Here are two theories:
1) The spirits in prison are fallen angels or demons. The spirits in prison cannot be holy angels because the holy angels have not sinned and are not imprisoned. And not all the fallen angels are imprisoned, of course, for the New Testament gives many examples of demonic activity on earth. That leaves a select group of demons who, unlike the their fellow demons, are held captive.
What might be a reason for some, but not all, of the demons to be imprisoned? Jude 1:6 gives us an important clue: “The angels who did not keep their positions of authority but abandoned their proper dwelling—these he has kept in darkness, bound with everlasting chains for judgment on the great Day.” Some fallen angels committed an egregious crime of some kind; Jude 1:6 does not give details, but the demons’ sin was related to how they “did not keep their own position but deserted their proper dwelling.” Revelation 9:1–12, 14–15, and 2 Peter 2:4 also speak of a group of wicked angels that are currently bound.
If the spirits in prison are fallen angels, the sin they committed could be the one in Genesis 6:1–4, which records the “sons of God” mating with the “daughters of men” and producing a race of giants, the Nephilim. If the “sons of God” were fallen angels, then the sin of Genesis 6 involved angels leaving the place where they belonged in an act of disobedience before the Flood—and that corresponds to what the apostle mentions in 1 Peter 3:19. It could be that the demons who cohabited with human women were imprisoned by God to prevent them from repeating that sin and to discourage other demons from trying it.
According to 1 Peter 3:19, Jesus “made proclamation” to these spirits in prison. The Greek word translated “proclaimed” or “preached” means “to publicly declare” or “to herald.” If the spirits are demons, then Peter says that Jesus went to the Abyss and proclaimed His victory to the fallen angels imprisoned there. They had lost, and He had won. The cross triumphs over all evil (see Colossians 2:15).
2) The spirits in prison are the human spirits of those who perished in the flood of Noah’s day. As for Christ preaching to them, there are three possible interpretations: a) Christ preached to them figuratively, in and through Noah, while they were in the flesh; b) Christ preached to them literally, being present with Noah through the Holy Spirit who inspired Noah to proclaim the message of coming judgment; and c) Christ preached to them literally in between His death and resurrection. According to each of these interpretations, the spirits are called such because they existed in a spiritual condition when Peter wrote; they were no longer in the flesh but lived in Hades/hell.