What does Matthew 10:33 mean?

Christ will acknowledge to His Father everyone who acknowledges to others that He is the Son of God (Matthew 10:32; John 3:16–18). In other words, when the time of judgment before God comes, Jesus will vouch for everyone who embraced Him as their Savior. He will stand alongside them, before God the Father, as a righteous witness to vouch for those who are His. The implication is that those who are His will be welcomed into eternity with the Father.

Now Jesus adds that the opposite is also true. He will refuse to acknowledge to God anyone who denies Christ to other men. Because human beings can only be declared righteous by faith in Jesus (John 14:6), those He denies will be denied by the Father, as well. The consequences will be eternal (John 3:36).

This statement inspires a great deal of fear, since it seems to suggest that anyone who denies their faith, on earth, will be lost. However, there are reasons to expect denying Christ to be a real temptation. For the apostles and early Christians, a simple denial that Jesus was the Son of God could have been the difference between life and death, between arrest or freedom, between feeding one's family or not. The stakes that come with being associated with Him will be high for these twelve apostles and for many others. Jesus, though, wants His followers to understand that the stakes of denying Him will be much higher than merely death on this side of eternity.

The full context of Scripture strongly suggests that a single, panic-driven denial of Jesus will not necessarily end a believer's opportunity to spend eternity with the Father. Christians are saved by God's grace through faith in Jesus, not by perfect performance in acknowledging Him (Ephesians 2:8–9). Peter will most famously deny Christ at a crucial moment because of his own fear of being arrested and killed (Matthew 26:69–74). After Jesus' resurrection and the arrival of the Holy Spirit, though, Peter will spend the rest of his life powerfully acknowledging Jesus to others (Acts 2).

Where this warning becomes more dire is in the lives of those who consistently, or easily, dissociate themselves from Christ for the sake of health, wealth, popularity, or freedom. Those who aren't willing to be associated with Jesus on earth won't be allowed to claim association with Him in eternity (Matthew 10:37; Mark 8:36).