“As long as a person is not a murderer, adulterer, or thief he would swear that he is righteous. How is God going to humble such a person except by Law? The Law is the hammer of death, the thunder of hell, and the thunder of God’s wrath to bring down the proud and shameless hypocrites. When the Law was instituted on Mount Sinai, it was accompanied by lightening, by storms, by the sounds of trumpets to tear to pieces that monster called Self-Righteousness. As long as a person thinks he’s right, he’s going to be incomprehensibly proud and presumptuous. He’s going to hate God, despise His grace and mercy, and ignore the promises in Christ. The Gospel, the free forgiveness of sins through Christ, will never appeal to the self-righteous. This monster of self-righteousness, this stiff-necked beast needs a big axe, and that’s what the Law is, a big axe.”
From his Commentary on St. Paul's Epistle to the Galatians.