Romans 5:20–21—Law increases sin; grace leads to eternal life.

Paul has traced the problem of sin back to Adam, and he has located the origin of justification by faith in God’s dealing with Abraham (chapter 4). The law as well plays an important role in salvation history, so where does it fit in? The law, Paul says, “came in” with a purpose.

We saw in verses 13 and 14 that sin was in the world before God gave the written law to Moses. So a law had to have been in effect throughout that time, and it was the law God has written on people’s hearts, as Paul explained in chapter 2. Whereas that law gives people only a general sense of God’s moral standards, the Mosaic law Paul now speaks of clarified those standards in such explicit detail that one of its effects was “to increase the trespass.”

Bring in the chains
The law increases sin in the same sense that the chains in football increase fourth downs. The ball may look close to the first-down marker until the officials bring in the chains to measure, showing the ball to be shy by inches. The Mosaic law clarified and made explicit God’s moral standards, revealing sin for what it is. The law did not create the sin any more than the chains caused a fourth down. Both the sinner and the team on the offense missed the mark.

Some people back then and still today have regarded the law as the solution to sin. By establishing rules and setting goals and expectations, they think they can motivate themselves and others to a more pure lifestyle. But God’s purpose for the law was not to solve sin but to convince sinners they are just like Adam, who rebelled against God’s declared will.

What Paul means is similar to what he said in chapter 3—the law makes people conscious of their sin and reveals their desperate need for grace (3:20–24).

Paul is not done with his treatment of the law, for in chapter 7 he will illustrate with agonizing detail the law’s failure to solve the sin problem. Craig Keener explains that “Paul must bring in the law’s condemning function (i.e., the law as a righteous standard, hence a criterion of judgment) to prepare for his later association of the law with death in 7:9—11.” And in the latter part of chapter 7 Paul will demonstrate the law’s weakness in the fight against sin.

The reigns of sin and grace
Paul again juxtaposes two competing dominions. In verse 17 it was death that reigned, whereas those saved by grace will reign in life through Christ. Now it is sin that reigned in death, whereas grace reigns through righteousness leading to eternal life through Christ. In both cases grace presides over the far superior kingdom.

Neither sin nor death can outdo grace, because when they increase grace abounds all the more. The dominion of grace is by far the stronger, forgiving and canceling sin and taking away the sting of death. Whenever sin tries to get the upper hand, grace “super-abounds” or “super-increases” with overwhelming power—the power of the eternal King who empowers grace.

If you would like to transfer your citizenship from the dominion of sin and death to the dominion of grace, all you need do is with a repentant heart reach out your hand to receive the free gift of righteousness through Jesus Christ (verse 17). God will immediately transfer you from the domain of darkness to the kingdom of Jesus Christ where you will find redemption and the forgiveness of sins (Colossians 1:13–14).

Why faith?
The only requirement to lay hold of God’s grace is faith. “Faith is the one human attitude that is the opposite of depending on oneself, for it involves trust in or dependence upon another. Thus, it is devoid of self-reliance or attempts to gain righteousness by human effort” (Wayne Grudem). Upon whom do we depend? The worthy One, who became flesh and dwelt among us, who is full of grace and truth, and from whose fullness we have all received grace upon grace (John 1:14–16).

“For by grace you have been saved through faith. And this is not your own doing; it is the gift of God” (Ephesians 2:8).