"There is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus."
We are in the midst of a key text for the biblical doctrine of justification, and we have seen that apart from the sinner's keeping the law of our Creator, a righteousness from God has been manifested in the gospel for all who believe, whether they are of Jewish or Gentile origin. Being apart from the law does not mean that this righteousness is contrary to the stipulations of God's law, for the Law and Prophets—the Old Testament Scriptures—bear witness to it. Instead, this righteousness is apart from the law of God because the fallen person does not attain it by keeping the law. This righteousness is not accomplished by conforming to God's law, so it is not something the old covenant system could provide to sinners under that covenant, such as David (Rom. 3:21; see 4:4–8). No, this righteousness from God is "through faith in Jesus Christ for all who believe" (3:22a). The only way to be seen as righteous by our Creator is to believe in Christ alone.
But why is righteousness by faith only (see 3:27–28), and why is it for all who believe and not just for the Jews who believe (v. 22a)? The answer goes back to Romans 1:18–3:20, where Paul argued that all (except for Jesus) have failed to obey the Lord, Jew and Gentile alike: "All have sinned and fall short of the glory of God" (3:22b–23). We have not kept the mandate to bear God's image in holiness (Gen. 1:26–27), for our sin has tarnished this image. We need Christ for transformation into the image of the Lord's glory because we have sinned and marred this glory (2 Cor. 3:18; Phil. 3:21). We do not obey God as we ought; we break His law time and again. This is true for all fallen children of Adam, and since the same malady afflicts all of us, only the same remedy—Jesus Christ—can cure all of us.
Justification by faith alone is necessary because of how far we have fallen, but faith is not the grounding or meritorious basis for our righteous status. This basis is "the redemption that is in Christ Jesus." Strictly speaking, the reason our Father declares a person righteous in His eyes is the work of the Savior, which itself is grounded in the grace of our triune God (Rom. 3:24). Our faith does not earn for us God's favor; rather, God's unmerited favor toward those whom He has chosen for salvation motivated the work of Christ, which we benefit from for the sake of our justification when we believe the gospel. John Calvin comments, "When therefore we are justified, the efficient cause is the mercy of God, the meritorious is Christ, the instrumental is the word [of God] in connection with faith."
Coram Deo
If justification were a meritorious reward that we earn because we have faith, we would have no assurance of peace with God. After all, our faith is not always strong, and until our glorification it is mixed with sin. No, the firm basis of our right status before the Lord is what Jesus has done, the redemption He purchased by living and dying for His people. When our faith is weak, we remain justified because it is Christ Himself who is the basis for God’s righteous verdict.