“For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God.”- 2 Corinthians 5:21
Justification comes from God’s grace alone (sola gratia) and is ours through faith alone (sola fide). But we cannot miss that the ground of our being declared righteous by God is due to the work of Christ alone (solus Christus).
To understand solus Christus, we need to consider again the two main covenants God has made with humanity. The first of these is the covenant of works, which was made with Adam as the representative of all people in Eden. Adam was promised life or death depending on his obedience to the Lord’s command not to eat of the Tree of the Knowledge of Good and Evil (we deduce that he would have earned eternal life if he had obeyed; Gen. 2:15–17; Rom. 5:12–21; see WCF 7.2). Of course, Adam failed, plunging his descendants into sin. But God does not change His holy demands, and all people remain obligated to keep the covenant of works even though it is impossible for us to meet this standard.
Our Creator would have been entirely just to leave all people in their condemnation, but out of His love and mercy He entered into a covenant of grace with a people of His choosing. In this covenant, God provides a way for us to be reckoned as those who have kept the covenant of works. But we are not the ones who actually keep the covenant, someone else does it for us — that is why it is a gracious covenant. Genesis 3:15 and the promise that a child of Eve will crush Satan and death is the first place this covenant is revealed in Scripture.
Christ, by virtue of His perfect life and atoning death, fulfills the covenant of works on our behalf, as seen in 2 Corinthians 5:21. On the cross, our guilt for failing to keep God’s covenant was imputed to Jesus, that is, our sin was reckoned to Christ’s account and condemned in the flesh. The Father “made him to be sin” (2 Cor. 5:21). But if this was all that happened, we would not be righteous before God but neutral, as Adam was before the fall. Jesus lived a life of flawless obedience (1 Peter 2:22), keeping the covenant of works, and the record of this one “who knew no sin” is imputed to us when we trust Him alone (2 Cor. 5:21). God reckons Christ’s righteousness to our account and, looking at us in Christ, sees a record of perfect obedience and declares us righteous in His sight.
Mankind’s failure to meet the Lord’s standard of perfection is an essential part of the gospel message, and the covenant of works informs us of His standard. Jesus did not come to give us our best life now or to bring us wealth and health today. He came to earn a righteousness for us that would overcome death and make us worthy of the new heavens and earth. Make sure God’s unattainable standards and the answer of His grace are part of your gospel presentation.
Passages for Further Study