For Christ also suffered once for sins, the just for the unjust, that He might bring us to God, being put to death in the flesh but also made alive by the Spirit, (19) by whom also He went and preached to the spirits in prison, (20) who formerly were disobedient, when once the Divine longsuffering waited in the days of Noah, while the ark was being prepared, in which a few, that is eight souls, were saved through water. (21) There is also an antitype which now saves us – baptism (not the removal of the filth of the flesh, but the answer of a good conscience toward God), through the resurrection of Jesus Christ, (22) who has gone into heaven and is at the right hand of God, angels and authorities and powers having been made subject to Him

The verses we study today were written by the apostle Peter. His point is clear but the details are very complex and the obscurity of these verses have occasioned many – almost universal – conflicting interpretations: they have served as the basis for the Catholic doctrine of purgatory and as foundation for the short lived inclusion in the Apostles creed that after Jesus Christ suffered and died He descended into hell – My older readers might have noticed the sudden disappearance of that statement from the creed. Who were the prisoners to whom Christ preached in the interval between death and resurrection? What did Christ proclaim? In short, these verses are not doctrinal.
But the purpose of this passage is clear; the faithful are called upon to bear witness to Christ in a hostile world where they can trust God to vindicate them just as Christ who suffered unjustly was vindicated by God through His resurrection and ascension to the right hand of God. Peter also uses the example of Noah who suffered in a hostile world but was vindicated by his delivery through the flood. Suffering in Peters time was linked to outward baptism or public confession of faith (this is not however a condition for salvation). They and we are called to give testimony to truth of the gospel. If we, in faith, bear witness, God will vindicate us.
Christ is our redeemer from sin and the faithful are not righteous outside of faith. Good works on the part of man are never sufficient but they and holy living are witness to our living faith. We are saved by Christ, not ourselves.