17-20 It’s better to suffer for doing good, if that should be God’s will, than for doing evil. For Christ also suffered for sins once for all, the righteous for the unrighteous, that he might bring you to God.  He was put to death in the flesh but made alive by the Spirit, in which he also went and made proclamation to the spirits in prison who in the past were disobedient, when God patiently waited in the days of Noah while the ark was being prepared. In it a few (that is, eight people) were saved through water.  21-22 Baptism, which corresponds to this, now saves you (not as the removal of dirt from the body, but the pledge of a good conscience toward God) through the resurrection of Jesus Christ,  who has gone into heaven and is at the right hand of God with angels, authorities, and powers subject to him.

Chapter 4 vs 1-2. Therefore, since Christ suffered in the flesh, arm yourselves also with the same understanding - because the one who suffers in the flesh is finished with sin, in order to live the remaining time in the flesh no longer for human desires, but for God’s will. 1 Peter 3:17-4:2 Christian Standard Bible

Peter had been reminding his readers that being a Christian can bring sufferings in this world even though they are living good lives rather than evil ones. How did he say we should look upon such sufferings? (Chapter 4:1-2)

He says that Christ knows what it is like to suffer in the body because He experienced that extremely when He died on the cross for sins we had done. We should therefore accept sufferings we go through as being an indication that we have put our flesh to death too – i.e. the old lifestyle of sin - in order to live the rest of our lives seeking to do God's will. It's as if we are saying “I'm done with sins! From now on I want to only live for God.” What is the Christian 'ceremony' that Peter refers to which pictures what he has been talking about? (vs 21-22)

People who became Christians were baptized. The act of being covered by water was symbolic of being buried, and then raised again. The apostle Paul said: “All of us who were baptized into Christ Jesus were baptized into his death. We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life.” (Romans 6:3-4) But notice how Peter points out that baptism only saves a person when it is linked with faith to what Jesus Christ did. Simply being baptized will not save anyone – especially if it doesn’t lead to turning away from sin.

Peter also pictured baptism as being like what happened in the days of Noah when God's wrath was poured out on the world by means of a flood. Noah and his family were saved through the water while the rest of mankind perished. The implication is that those who are not saved by Christ will also perish on that day when God's wrath is again poured out on a sinful world. But, in saying this, Peter also adds something that the Bible doesn’t tell us much about. He says Jesus was put to death in the flesh but made alive by the Spirit, in which he also went and made proclamation to the spirits in prison who in the past were disobedient, when God patiently waited in the days of Noah while the ark was being prepared. What can that mean?

Hades is regarded as the place of the spirits of people who've died and who are awaiting the final judgement. Some suggest that Jesus preached His victory over death to those who had died in Noah's generation to give them 'a second chance'. Others say that by proclaiming His work of salvation He was just confirming their guilt and judgement. The important fact to take hold of, though, is that those people died in the flood because of their disobedience, despite God's great patience. They were not willing to be done with sin! And that's the point Peter was making to everyone who is baptised into Jesus and who calls on God for that good conscience. We need to live from then on as those who have finished with sin. Are we done yet?