“Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.” (Romans 3:19–20, KJV 1900)
In our country there are many laws. Congress has established laws. State legislatures have established laws. Local municipalities have established laws. Yet, what have the laws accomplished? They do curb the behavior of lawless people to some extent. Yet, the majority of people still break speed limits or coast through stop signs, at least on occasion. One thing the law will absolutely do is silence the lawbreaker. Confronted with the law, the lawbreaker cannot say he did not break the law.
Paul has just gone to great lengths to deal with the depravity of man and that he is a transgressor. Both the Jew who was under the law and the Gentile who shows that the work of the law is written on his heart, transgresses these very laws. Now Paul gives a grand summary of man’s problem and reveals one great purpose of the law.
Paul indicates that through the law man comes to a correct and precise knowledge of sin and this knowledge will silence every mouth. Why will men be silenced? It is because there is not one person who ever lived, except Jesus, that perfectly kept the entirety of the law. Thus, no person will be justified before an infinitely holy God based upon the works of his own life.
As we will see, man has only one hope for justification and that is faith in Jesus Christ alone. If you meet a person who thinks they can justify themselves by the good works of their life, ask them to consider the law. My guess is that they have broken most of the Ten Commandments either overtly or by the attitudes of their hearts. The law will silence their boasting.