Question: "Why is justification by faith such an important doctrine?"
Answer: The teaching of justification by faith is what separates biblical Christianity from all other belief systems. In every religion, and in some branches of what is called “Christianity,” man is working his way to God. Only in true, biblical Christianity is man saved as a result of grace through faith. Only when we get back to the Bible do we see that justification is by faith, apart from works.
The word justified means “pronounced or treated as righteous.” For a Christian, justification is the act of God not only forgiving the believer’s sins but imputing to him the righteousness of Christ. The Bible states in several places that justification only comes through faith (e.g., Romans 5:1; Galatians 3:24). Justification is not earned through our own works; rather, we are covered by the righteousness of Jesus Christ (Ephesians 2:8; Titus 3:5). The Christian, being declared righteous, is thus freed from the guilt of sin.
Justification is a completed work of God, and it is instantaneous, as opposed to sanctification, which is an ongoing process of growth by which we become more Christlike (the act of “being saved,” cf. 1 Corinthians 1:18; 1 Thessalonians 5:23). Sanctification occurs after justification.
Understanding the doctrine of justification is important for a Christian. First, it is the very knowledge of justification and of grace that motivates good works and spiritual growth; thus, justification leads to sanctification. Also, the fact that justification is a finished work of God means that Christians have assurance of their salvation. In God’s eyes, believers have the righteousness necessary to gain eternal life.
Once a person is justified, there is nothing else he needs in order to gain entrance into heaven. Since justification comes by faith in Christ, based on His work on our behalf, our own works are disqualified as a means of salvation (Romans 3:28). There exist vast religious systems with complex theologies that teach the false doctrine of justification by works. But they are teaching “a different gospel—which is really no gospel at all” (Galatians 1:6–7).
Without an understanding of justification by faith alone, we cannot truly perceive the glorious gift of grace—God’s “unmerited favor” becomes “merited” in our minds, and we begin to think we deserve salvation. The doctrine of justification by faith helps us maintain “pure devotion to Christ” (2 Corinthians 11:3). Holding to justification by faith keeps us from falling for the lie that we can earn heaven. There is no ritual, no sacrament, no deed that can make us worthy of the righteousness of Christ. It is only by His grace, in response to our faith, that God has credited to us the holiness of His Son. Both Old and New Testaments say, “The just shall live by faith” (Habakkuk 2:4; Romans 1:17; Galatians 3:11; Hebrews 10:38).