What does 1 Peter 4:18 mean?

Peter references Proverbs 11:31 to support his point from in the previous verse. God judges His children during life on earth, in order to strengthen and purify our faith. Those who reject Christ can expect much worse. Again, we need to be careful not to insert meaning into this passage. Peter is not saying that Christians are those who try really hard to be saved, and then just barely make it into heaven by their best efforts. We only make it into heaven by Jesus' perfect effort and perfect payment on the cross for all of our sin (1 Peter 3:18). Peter is saying that eternal salvation through faith in Christ comes "with difficulty" in this life on earth. Our loving Father treats us as children who need discipline to learn to trust Him, to learn to walk in His way.

In other words, God calls us righteous in Christ, then uses hardship in our lives to increase our trust in Him, to make us more and more like Christ.

But what will become of the ungodly and the sinner? Christians may often think of themselves as being sinners and ungodly people. Our actions might suggest that. But as used in this context, Peter isn't talking about believers; he is talking about those who "disobey the gospel of God" (1 Peter 4:17). So, if God allows the righteous in Christ to experience such hardship out of His love for us, what kind of hardship will come to those who reject God by rejecting faith in Jesus? The implied answer is that it will be much more terrible for them than it ever will be for us.