What does Mark 9:49 mean?

In Mark 9:48, Jesus says that sinners will suffer in unquenching fire. Here, He says everyone will experience the flames. Sinners will face the consuming fire (Deuteronomy 4:24; Hebrews 12:29) of God's judgment at the Great White Throne Judgment (Revelation 20:11–15). Similarly, Paul speaks about how believers' good works will be tested by fire to see if there is anything pure enough to remain. If there is, that person will receive a reward. If not, they will come out with their lives (1 Corinthians 3:12–15).

This purification ritual will be performed at what is called the "Bema Seat of Christ." It is there that Christians will give an account for their actions on earth (Romans 14:10–12) and receive what we deserve (2 Corinthians 5:10).

Many Christians are fearful of this judgment, particularly that others will hear about our sins. Jesus' words that "nothing is…secret except to come to light" (Mark 4:22) is only inspiring if the secret isn't yours! But this judgment is the point where we will finally understand our place in God's kingdom. We will see evil as it really is, and be eternally grateful for Jesus' forgiveness. We will realize, like adolescents growing into mature adults, that other people are usually more interested in their own lives than ours. And we will gain God's heart, valuing righteousness and rejecting the evil we once did (1 John 3:2).

Those who do not accept Christ have every reason to fear the flames of judgment. For Christians, it will be the final shedding of our sinful lives and the culmination of the Holy Spirit's purifying work in us.