The worst fault in modern preaching, my dear friends, is this, that the sermons lack point and purpose; and this fault can be noticed particularly in the sermons of modern preachers who are believers. While unbelieving and fanatical preachers have quite a definite aim, — pity, that it is not the right one! — believing preachers, as a rule, imagine that they have fully discharged their office, provided what they have preached has been the Word of God. That is about as correct a view as when a ranger imagines he has discharged his office by sallying forth with his loaded gun and discharging it into the forest; or as when an artilleryman thinks he has done his duty by taking up his position with his cannon in the line of battle and by discharging his cannon. Just as poor rangers and soldiers as these latter are, just so poor and useless preachers are those who have no plan in mind and take no aim when they are preaching. Granted their sermons contain beautiful thoughts; they do not, for that matter, take effect. They may occasionally make the thunders of the Law roll in their sermons, yet there is no lightning that strikes. Again, they may water the garden assigned to them with the fructifying waters of the Gospel, but they are pouring water on the beds and the paths of the garden indiscriminately, and their labor is lost.
Neither Christ nor the holy apostles preached in that fashion. When they had finished preaching, every hearer knew: He meant me, even when the sermon had contained no personal hints or insinuations. For instance, when our Lord Christ had delivered the powerful, awful parable of the murderous vine-dressers, the high priests and scribes confessed to themselves: He means us. When the holy Apostles Paul, on a certain occasion, had preached before the profligate and unjust Governor Felix concerning righteousness, temperance, and the Judgment to come, Felix perceived immediately that Paul was aiming his remarks ant him. He trembled, but being unwilling to be converted, he said to Paul: "Go thy way for this time; when I have a convenient season, I will call for thee." But he never did call him. He had heard the sermon suited to his spiritual condition, and Paul's well-aimed remarks had struck home.
The reason, then, my dear friends, why in the Lutheran congregations of our former home country Germany unbelieving preachers are nearly always in the ascendancy is unquestionably this: the sermons of the Christian preachers are aimless efforts. Unbelievers are increasing in the congregations about as fast as the Christian preachers are increasing, of whom there are considerably more now than when I was young. Why do they accomplish nothing? Oh, would to God that these dear men had the humility to sit down at Luther's feet and study his postils! They would learn how to preach effectively. For the Word of God, when preached as it should be, never returns void.
from C.F.W. Walther, "Law and Gospel, Twelfth Evening Lecture" (December 12, 1884)