When Adam and Eve were created, they stood in a moral relationship with God, their Creator. They possessed a duty of obedience to Him without any inherent claim to reward or blessing for such obedience. In His love, mercy, and grace, however, God voluntarily entered into a covenant with His creatures by which He added a promise of blessing to His law. This was not a covenant of equal partners, but one that rested on God’s initiative and His divine authority.
The original covenant between God and humankind was a covenant of works. In this covenant, God required perfect and total obedience to His rule. He promised eternal life as the blessing of obedience, but threatened mankind with death for disobeying God’s law. All human beings from Adam to the present are inescapably members of this covenant.
People may refuse to obey or even acknowledge the existence of such a covenant, but they can never escape it. All human beings are in a covenant relationship to God, either as covenant breakers or covenant keepers. The covenant of works is the basis of our need of redemption (because we have violated it) and our hope of redemption (because Christ has fulfilled its terms for us).
A single sin is enough to violate the covenant of works and make us debtors who cannot pay our own debt to God. That we, after even a single sin, have any hope of redemption is due to God’s grace and God’s grace alone.
The rewards we will receive from God in heaven are also acts of grace. They are God’s crowning of His own gracious gifts. Had Adam been obedient to God’s covenant of works, he would only have achieved the merit that comes by virtue of fulfilling the covenant agreement with God. Because Adam fell into sin, God, in His mercy, added a new covenant of grace by which salvation became possible and actual.
Only one human being has ever kept the covenant of works. That person was Jesus. His work as the second or new Adam fulfilled all the terms of our original covenant with God. His merit in achieving this is available to all who put their trust in Him.
Jesus is the first person to get into heaven by His good works. We also get into heaven by good works—the good works of Jesus. They become “our” good works when we receive Christ by faith. When we put our faith in Christ, God credits the good works of Christ to our account. The covenant of grace fulfills the covenant of works because God graciously applies the merit of Christ to our account. Thus by grace we meet the terms set forth in the covenant of works.
R. C. Sproul, Ed., The Reformation Study Bible: English Standard Version (2015 Edition), (Orlando, FL: Reformation Trust, 2015), 16.