Isaiah 62:10 “Prepare the way for the people. Build up the highway. Go, go through, Clear it of stones. …After the godly and honest men have preached, they must work at driving off the ungodly preachers. “Beware of false prophets” (Matt. 7:15). It is their endeavor to put away offenses, ungodly teachings, so that the people may not be offended. It is our task to see to it that a godly people, well taught, can simply proceed on the way without a stumbling block. The chief teaching is already present. There remains the one endeavor, namely, that the teaching be retained. To guard possessions is no less a virtue than to acquire them. Take care that some sectarian does not come who will impose upon you. Thus I, Martin Luther, was in four dangers, and yet, beyond my own planning, I was set free by God. When Satan sees us standing firm in the Word, he begins to set another plan before us and tries to lead us into it, so that the whole world will perish by our counsel. He has a thousand tricks.
Lift up an ensign over the peoples. Thus Ps. 4:6 reads: “Lift up the light of Thy countenance upon us.” Raise up the banner. Set yourselves in battle array, and do not be sleepy. For the whole world is against us. The Word is a fighting word. In the first place, by teaching it one wages war against the ungodly. Then that which is taught is attacked by the ungodly. Do not be smug and do not sleep, but lift up an ensign, since the pastors must be on guard, lift up the Word, study, and apply themselves to defending the Word. Therefore let us not be smug, for Satan does not sleep. (Luther’s Works, v. 17, pages 350).