The law did not teach a living, saving knowledge; but, by its rites and ceremonies, especially by its sacrifices, it pointed to Christ, that they might be justified by faith. And thus it was, as the word properly signifies, a servant, to lead to Christ, as children are led to school by servants who have the care of them, that they might be more fully taught by Him the true way of justification and salvation, which is only by faith in Christ.
And the vastly greater advantage of the gospel state is shown, under which we enjoy a clearer discovery of Divine grace and mercy than the Jews of old. Most men continue shut up as in a dark dungeon, in love with their sins, being blinded and lulled asleep by Satan, through wordly pleasures, interests, and pursuits.
But the awakened sinner discovers his dreadful condition. Then he feels that the mercy and grace of God form his only hope. And the terrors of the law are often used by the convincing Spirit, to show the sinner his need of Christ, to bring him to rely on his sufferings and merits, that he may be justified by faith.
Then the law, by the teaching of the Holy Spirit, becomes his loved rule of duty, and his standard for daily self-examination. In this use of it he learns to depend more simply on the Saviour.