73. Q. 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, but only as it is an instrument by which he receiveth and applieth Christ and his righteousness (John 1:12; Philippians 3:9; Galatians 2:16).
Who will become a child of God? The one who is “in Christ.” Who will get “into Christ”? The one who receives Christ by faith, or, according to the original Greek, believing “into” him. John writes, “But to all who did receive him, who believed in (literally, “into”) his name, he gave the right to become children of God” (John 1:12).
Faith which places the sinner “in Christ” is not merely an acknowledgment that there was a historical figure named Jesus of Nazareth who embarked on an itinerant ministry which lead many first century Jews to conclude that he was the Anointed One (“Christ”) proclaimed by the Old Testament prophets. Faith in Christ does begin with such knowledge, even assenting to the truthfulness of such a proposition, but it must also result in a willingness to rest on the righteousness which Christ is proclaimed in the gospel message to have earned by his flawless observance of the law of Moses which has at its heart the moral law of God, confessing that by one’s own observance of God’s law he will not be able to earn for himself the same kind of inherent righteousness. As Paul writes in Galatians 2:16:
“yet we know that a person is not justified by works of the law, but through faith in Jesus Christ. So we also have believed in (again, “into”) Christ Jesus in order to be justified by faith in Christ, and not by works of the law, because by works of the law no one will be justified.”
So being found in Christ depends on having the righteousness of Christ which comes from God, and having the righteousness which comes from God depends on faith. In Philippians 3:9 it is written, “and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith.” So we see that when faith is imputed as righteousness, faith is not the thing that makes a person inherently righteous, but rather it is simply what the Westminster Divines call in Q&A #73 of the Larger Catechism, “an instrument by which he receiveth and applieth Christ and his righteousness.”