But since that which I (new nature) do not desirously will, this I (old nature) do, I (new nature) together say with the law that [the law] is proper. (Romans 7:16)
The struggle within the grace believer between the new nature and the old nature demonstrates that the law is a proper standard. The old nature produces what the new nature does not desire in regard to the law.
Those who seek to be righteous through law must keep every aspect of that law, for whoever stumbles in one part is guilty of all (James 2:10). The woman who will not permit a foul word to proceed from her mouth, does she gossip? The man who upholds the commandment against adultery, does he kill without cause?
We cannot seek to be justified by law in one aspect while permitting its violation in another. We cannot say, “You shall not steal,” except when one is starving. Yet when we seek to live by law, the sin nature within us produces the very things we do not desire to do, thereby demonstrating that the law is proper, but we are incapable of living by it.