St. Paul pointed out a basic Scriptural — and logical — fact, when he said:
“For not the hearers of the law are just before God, but the doers of the law shall be justified” (Rom. 2:13).
Many people suppose that God gave us the Ten Commandments to help us to be good. The fact is, however, that He gave them to show us that we are bad. Rom. 3:20; Gal. 3:19 and a hundred other Bible passages teach this clearly.
How can the Law be of any advantage to a law-breaker? How can it justify us unless we keep it — perfectly?
Do you recall the woman caught in adultery, in John 8? She was a Jewess. She was better off than the Gentiles, for she had the law of Moses to show her right from wrong, but this didn’t justify her; it condemned her. So her “advantage” turned out to be a serious disadvantage, for “not the hearers of the law are just before God, but the doers of the law shall be justified.”
James 1:23,24 says that one who knows the Law but doesn’t obey it, is like a man looking into a mirror, seeing his dirty face, and then walking away without doing anything about it. This is why Rom. 2:14,15 declares that the consciences of the heathen confirm what the Law says, “their thoughts the meanwhile accusing, or else excusing one another.”
Those in heathen lands know that it is wrong to lie and steal and commit adultery, yet they know nothing about the law of God, or the Ten Commandments. How, then, do they know that these things are wrong? God made them with this knowledge; He gave to them, and to us all, conscience, a sense of blameworthiness in doing wrong.
How good to know the One who has paid the penalty for our sins so that our hearts may be cleansed from “an evil conscience” (Heb. 10:22)! source