Question: Since no one can keep the law, what is its purpose?
Answer: That we may know the holy nature and will of God, and the sinful nature and disobedience of our hearts; and thus our need of a Savior. The law also teaches and exhorts us to live a life worthy of our Savior.
Commentary: After God gave the promise to Abraham, he gave the law to Moses. Why? Simply because he had to make things worse before he could make them better. The law exposed sin, provoked sin, condemned sin. The purpose of the law was…to lift the lid off man's respectability and disclose what he is really like underneath—sinful, rebellious, guilty, under the judgment of God, and helpless to save himself. And the law must still be allowed to do its God-given duty today. One of the great faults of the contemporary church is the tendency to soft-pedal sin and judgment…. We must never bypass the law and come straight to the gospel.
To do so it to contradict the plan of God in biblical history…. No man has ever appreciated the gospel until the law has first revealed him to himself. It is only against the inky blackness of the night sky that the stars begin to appear, and it is only against the dark background of sin that the gospel shines forth. Not until the law has bruised and smitten us will we admit our need of the gospel to bind up our wounds. Not until the law has arrested and imprisoned us will we pine for Christ to set us free. Not until the law has condemned and killed us will we call upon Christ for justification and life. Not until the law has driven us to despair of ourselves will we ever believe in Jesus. Not until the law has humbled us even to hell will we turn to the gospel to raise us to heaven.