In Mark 2:1-12, Jesus famously healed the paralytic, a man lowered on his mat through someone’s roof because of the crowd. Before Jesus restored his legs, however, he restored his soul, declaring the man’s sins forgiven. Some folks in the crowd fussed at Jesus for saying such a thing because only God himself can forgive a person’s sins. Therefore, Jesus told the man to take up his mat and walk home, in full view of the crowd. To everyone’s amazement, he did. The visible miracle (the healing of his legs) authenticated the invisible miracle (the forgiveness of his sins). In a dramatic display of his own power and authority, then, Jesus made the man’s salvation visible to everyone.

This story teaches us a lot about Jesus, but it also illustrates how God wants a believer’s salvation to be made visible in our day, too. He wants it to be verifiable. He wants it to be evidence by a changed life. The theological word is “sanctification,” which means to be set apart. This message looks at the doctrine of sanctification—the process by which God shapes a believer’s character over time to be more like Christ’s. While justification speaks of the beginning of our salvation, sanctification speaks of the continuing of our salvation. Like the two natures of Christ, they are distinct theological realties, but they cannot be separated.

Justification is about Christ’s work for us on the cross. Sanctification is about Christ’s work in us by the Holy Spirit. Justification is about Christ’s completed work in making us his children forever. Sanctification is about Christ’s continuing work in making us godly in life. Justification is about removing the penalty of sin in our lives. Sanctification is about breaking the power of sin in our lives. Justification is about forgiveness, so that we can come to God. Sanctification is about holiness, so that we can become like God (in character). Justification calls us to believe. Sanctification calls us to behave.

John Calvin explained the relationship between justification and sanctification using the sun as an illustration. He said the sun’s heat and the sun’s light are two distinguishable things. They are not the same, but they are always found together. They both flow from the nature of what the sun is. Moreover, we cannot have the sun’s heat without the suns’ light in the same way that we cannot have justification without sanctification.

Sanctification, then, is progressively growing in the grace we have freely received in Christ. It is the continuing work of God in the life of the believer, making us holy in practice, not merely in position. As Maxie Dunham has said, “We don’t buy a violin today and expect to give a concert in Carnegie Hall tomorrow. Similarly, we may be converted to Christ in a moment, but…walking as a Christian requires discipline and is a lifelong undertaking. As Christians, we do not emerge from our conversion fully grown; we must grow.” The Apostle Peter would agree: “But grow in the grace and knowledge of our Lord and Savior Jesus Christ” (2 Peter 3:18). In short, belief behaves.

When we embrace Jesus as the Savior who justifies us, we are at the same time embracing Jesus as the Lord who sanctifies us. The key to sanctification is living up to what we have already attained in Christ (cf. Philippians 3:16).