Paul's own words could make it sound as if the law were the villain. If sinful passions came "by the law," and believers needed to be delivered from it, is the law itself evil? Paul raises the objection so he can answer it. The first question opens the topic; the second states the wrong conclusion plainly. Gill reasons that since "the law is so useful to discover, and so to discountenance sin," it "cannot be sin, or sinful."

Paul answers, "God forbid." Then he explains: "I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet" (Romans 7:7). The fault lay with sin, which took "occasion by the commandment" and "wrought in me all manner of concupiscence" (Romans 7:8). His conclusion: "Wherefore the law is holy, and the commandment holy, and just, and good" (Romans 7:12).

"Thou shalt not covet" is the last of the Ten Commandments (Exodus 20:17), which Barnes cites here. It reaches past outward actions to the desires of the heart. Barnes says the Law "fixes bounds to his desires, and teaches him what is right and what is wrong."

In Greek, "lust" (epithymia, desire) and "covet" (epithymeo, to desire) are the noun and verb of the same word family. Paul is saying he would not have recognized wrong desire as sin unless the law had said, in effect, "Thou shalt not desire." Barnes also points to Romans 3:20: "by the law is the knowledge of sin."

Paul's answer protects God's character. The law is "the law of God" (Romans 7:22), and Paul calls it "holy, and just, and good" (Romans 7:12). Its work is to show sin for what it is. Matthew Henry pictures it this way: "As that which is straight discovers that which is crooked," the law reveals what is bent in us.

But showing sin is not the same as curing it. The rest of Romans 7 traces how sin uses even a good commandment, until Paul cries for deliverance (Romans 7:24). The cure comes from God Himself: "what the law could not do... God sending his own Son" did (Romans 8:3).