1 Peter 3 v 19 says, So he went and preached to the spirits in prison, those who disobeyed God long ago
To whom does this verse refer? The fallen angels or the spirits of man who disobeyed God?
There are some who believe it is saying something that contradicts other scriptures. My answer is what I find to be most reasonable in the light of other scriptures.
Some say that Jesus did this preaching while he was in the grave, or after his ascension into heaven. That would mean it could refer to “fallen angels” or disobedient spirits of people. The problem with this theory is that nothing in scripture indicates that preaching to angels would change anything. Nor would preaching to the spirits of dead people (who were disobedient in the days of Noah) do any good, since all are to be judged based on what was done during their life on earth. (2 Corinthians 5:10; Hebrews 9:27) Because this kind of preaching would be of no value, I doubt that is what Peter meant.
So what do I think he meant? Keeping this in context, in verse 18 he mentions the Spirit. It was by this Spirit that he preached to those disobedient in the days of Noah. The reasonable conclusion is that when Noah preached to those people who were alive in his day, and disobedient, he was preaching by the authority of the Spirit and of Jesus. Noah did the actual preaching to people who were alive in his day and able to make choices. Although he was the physical instrument of the preaching, it was still Jesus through the Spirit that was preaching to them in the person of Noah. An example I gave in my class was from the art world. Many works are signed by, and attributed to, Rembrandt. There is strong evidence that many of those works bearing Rembrandt’s signature were actually painted by his students. He may not even have laid on any of the paint other than his signature. But it was Rembrandt’s concept and actual design for the painting; the filling in of the details (the paint over the sketch) was done by someone else at his direction. In the same way, Noah preached but the design was from Jesus and the Spirit of God.
That would mean that the “spirits in prison” were actual living people imprisoned by sin. They were alive at the time of the preaching, although they are now dead. They had the opportunity to repent then, but that opportunity ended with their death in the flood. But for those who are living now, just like Noah and his family were saved by the water, so immersion in water now saves us by the resurrection of Jesus Christ.