How foolish them, is a preacher who thinks: “Now I will let loose the thunder of the Law. I will describe hell in all its detail and paint them a real picture of damnation, and then they will shape up!” That will not improve the people at all. That has to happen in its own time, so that secure sinners are alarmed and become poor, contrite sinners. But the Law does not produce a change of heart, love of God, and love of one’s fellow human being. If anyone is motivated by the Law to do certain good works, he does them only because he is forced, just as the Israelites had to be forced by the covenant of the Law.
Law & Gospel: How to Read and Apply the Bible by C. F. W. Walther (A Reader’s Edition)