Q. 73. How doth faith justify a sinner in the sight of God?
A. Faith justifies a sinner in the sight of God, not because of those other graces which do always accompany it, or of good works that are the fruits of it, nor as if the grace of faith, or any act thereof, were imputed to him for his justification (Romans 4:5; 10:10); but only as it is an instrument by which he receiveth and applieth Christ and his righteousness.
Believing is not a good work. It earns nothing. If there were such a thing as a righteous person other than Jesus Christ, there would be no need to impute his righteousness to him. For this hypothetical person who earns righteousness by his own good works, having Christ’s righteousness imputed or credited to him would be superfluous, redundant, and unnecessary.
Christ did not come to call those who think their righteousness is good enough. God did not send his Son to die for those who never come to admit that they deserve to die because of their sin. In Romans 4:5, Paul describes God as “him who justifies the ungodly.” The ungodly one who despairs of his inability to earn righteousness by his good works is the kind of person whom God justifies, or declares righteous in his sight.
In this same passage, Paul explains that “his [the ungodly person’s] faith is counted as righteousness.” This is the biblical doctrine of imputation, and Paul elaborates on it in the rest of his sentence which concludes in verses 6 -8: “… just as David also speaks of the blessing of the one to whom God counts [imputes] righteousness apart from works: ‘Blessed are those whose lawless deeds are forgiven, and whose sins are covered; blessed is the man against whom the Lord will not count [impute, KJV] his sin.’” As you see, the Bible teaches that while a man’s faith may in one sense be “imputed,” or “counted” as righteousness, in a greater sense, what is really going on is that Christ’s righteousness is being imputed to the ungodly believer–the righteousness of Christ is counted as the righteousness of the ungodly believer. It is a careless misreading to interpret the Bible as teaching that God imputes faith to the ungodly; rather, God imputes the righteousness of Christ to him.
What, then, is the source of this faith by which we are justified by the imputed righteousness of Christ? “For with the heart one believes and is justified, and with the mouth one confesses and is saved” (Romans 10:10). In the song, “Rock of Ages,” Christians sing, “Nothing in my hand I bring/Simply to the cross I cling.” It is not the work of our hands by which we are justified, but the gracious gift of faith which emerges from a regenerate, spiritually living heart which has been newly freed from sin and empowered to rest on the finished work of his righteous Savior who has been crucified and risen for him. We may be justified by a righteousness that is not our own, but that righteousness is received by a faith that is very much our own, graciously enabled by the power of the Holy Spirit.
Answer #73 of the Westminster Larger Catechism, then, further denies that the faith by which he is justified was not imputed to him—it was not the faith of another, but his own faith which arises by God’s grace from his own regenerate heart. His faith is the fruit grown on the good tree of his own regenerate heart.