What does 1 Peter 4:6 mean?
Peter has written that unbelievers, who spend their lives seeking their own pleasure, resent and abuse Christians, who spend their lives seeking God's will even at the cost of their own comfort. In the previous verse, Peter assured Christians that a judgment of all people was coming. Those who rejected Christ and abused Christians would give an account and be judged by Christ.Verses 5 and 6 answer one of history's most common excuses, as made by pleasure-seekers: "Why waste your whole life doing God's will if you're just going to be dead in the end? You only live once (YOLO!), so get all the pleasure you can get!" Peter insists that is not the case. There is another life coming, and there will be a judgment.
So, when Scripture says the gospel was preached to those who are dead, it means to those who have died after trusting in Christ. Their choice to live for God, to suffer in their bodies for Christ's sake while alive, lead to their opportunity to live in the spirit in the next life even as God Himself does. Christians should be encouraged, and continue to encourage each other (Hebrews 10:24–25), that our suffering for Christ and commitment to Him is not in vain.