God is slow to judge and during that time he sent Noah to warn the world before sending such severe judgment. He did not leave that generation without a witness against their wickedness but spoke to them through his prophet. The Lord always warns before he judges, for he wishes to show his reasonableness, in contrast to the unreasonableness of sin.
Any interpretation of these verses, which understands Christ to have preached to the dead as a disembodied spirit himself, is contrary to the analogy of faith and therefore erroneous. The word ‘preached’ refers to the preaching of the gospel and cannot refer to the announcement of condemnation on those who were already lost. But what else could be said to the dead, for there is no second chance to repent given to men after death, and no further offer of pardon can be made. ‘It is appointed unto men once to die, and after this the judgment.’ If you die unregenerate ad unsaved, there is no second chance. There is no purgatory. The Roman Catholic doctrine of purgatory is built on a complete misinterpretation of this passage, interpreting it in such a way that it contradicts all the rest of Scripture. In addition, the passage only mentions one group of people from the past – those living in the time of Noah. If Christ went and preached to those who were dead spirits, why should he limit his preaching to this group only? A variant on this interpretation has Christ going and preaching to the righteous dead, that is, to Abraham, Isaac, Jacob, and all other Old Testament believers. The idea is that he took them from the abode of the dead and brought them to heaven. But Peter describes those whom Christ preached to as disobedient which could not apply to Old Testament saints, and again he only mentions those living in the time of Noah not all other believers from the past. The phrase which follows in verse 20, ‘which sometime were disobedient’, makes clear that the preaching took place before they came to be captive spirits in prison. Nor does Peter say that they were released from prison. If we add the word ‘now’, the sense becomes clearer – ‘unto the spirits now in prison’. It took hundred and twenty years to build, and there was an antagonistic population all around, sneering and jeering and scorning, and probably doing all they could to hinder the construction of the ark. But Noah and his family, with perhaps such help as they could pay or muster, built it over that time. A hundred and twenty years of patience on the part of Noah. A hundred and twenty years of sustaining antagonism and unbelief, by which Christ preached in Noah's generation, through him. Many pictures can be derived from that. Noah and his family left the old life behind, and were brought into a new life, a new humanity, a new mankind, a new beginning. So his suffering brought about a new start, a new blessing, and a preservation of the race.