Human beings from every time and place almost universally believe that they are saved through their doing of good works. In fact, only biblical Christianity teaches that the salvation of sinners is not based on the merit that accrues to their good deeds.
From a biblical perspective, it is understandable that people would believe their own good works will earn them a place in heaven. After all, God’s first covenant with human beings, the covenant of works, granted eternal life based on perfect obedience to its demands. Adam would have received everlasting life for himself and his descendants if he had not sinned (Gen. 2:15–17; Rom. 5:12–21). As children of Adam, all people have at least a vague memory of that covenant that informs their beliefs. Furthermore, all people, no matter how strenuously they claim otherwise, know that there is a God who makes demands and holds us accountable (Rom. 1:18–3:20).
As we will see, our salvation is actually dependent on good works, but not the good works of sinners. Instead, only the good works of Christ are the basis of our being found righteous in the sight of God (2 Cor. 5:21). The point is that God demands perfect obedience to His law, and that is why Christ’s obedience can justify us. Our obedience cannot make us righteous in His sight because we cannot obey Him perfectly.
Two strands of biblical teaching come together to tell us this. First, the law that God gave to Israel holds out a theoretical possibility of salvation to us. Keeping the law will bring life, and the keepers of the law will be justified, as Paul says in today’s passage (Rom. 2:13; see Lev. 18:5). But Paul also says that Jews cannot be justified by keeping the law, even those Jews who in the main conform to its requirements (Rom. 3:19–20; Phil. 3:2–11). How can it be that keeping the law will make us righteous in God’s sight and that Jews who keep the law cannot stand on their obedience to make them righteous before God? The only answer is that when it comes to our justification—God’s legal declaration that we are righteous in His sight—keeping the law can make us righteous only if we never fail to obey it.
Second, Paul tells us that the reason we cannot be justified by keeping the law has nothing to do with the law in itself. The problem is our fallenness (Rom. 7:7–25). Our sin makes us unable to obey the law perfectly, and that is why the law cannot justify us.