As Rev. Scott Keith with the 1517 Legacy Project does presentations all around the country on the need for clear distinction between Law and Gospel, he is asked one question more than any others. The question is “where can I get this stuff on a regular basis?” And . . . 99% of people who ask this question is already attending a church. To serve the necessity of growing in our understanding of this eternally crucial need, here is some instruction from Martin Luther about the “The voice of one crying in the wildnerness (Isaiah 40:3).”
By this prophecy Isaiah promises a new kind of teaching beyond that which had been in vogue heretofore. For in this way the evangelists begin. The voice of one crying. It is as if he were saying: “The preaching of the Law was a muttering, incomplete and unpleasant to all ears, and produced nothing but hypocrites. But here comes a voice, a clear and complete and universal proclamation which purely and joyously and most loudly declares that the warfare is ended and that sins are forgiven.” This is received from “a voice,” that is, through the public preaching of the Word. It must be heard and recieved from a speaking voice. Away with our schismatics, who spurn the Word while they sit in corners waiting for the Spirit’s revelation, but apart from the voice of the Word! They say one must sit still in a corner and empty the mind of all speculations, and then the Holy Spirit will fill it. The sophists also taught this. In vain, however, do we rely on this, and that for two reasons. In the first place, because we are not able to empty our souls of speculations. The devil will provide you with many thoughts. In the second place, because the flesh has not yet been killed in you. When you have heard the Word, you earnestly kill the flesh and empty your soul. It will happen in no other way. No one becomes spiritual without this voice. Away with all Enthusiasts (those who trust God will work apart from the Word and Sacraments). Take note: The beginning of all spiritual knowledge is this voice of one crying, as also Paul says, Romans 10:14: “How are they to believe . . . without a preacher?”
The voice of one crying, that is, a new kind of teaching which should be proclaimed everywhere. In the wilderness. This voice is sent forth in the wilderness both by the preacher himself and by the hearers. By contrast, wilderness is placed opposite the teaching of the Law. For like a jail, a wall, and a city, the Law secures and fences us in. The voice of the Gospel, however, is a free wilderness, open to all, public, and unrestrained like a wilderness. There is indeed a limitation about the Law, but the teaching of the Gospel is most free and most unrestrained. Hence all these words are as by contrast set against the teaching of the Law. The voice of one crying in the wilderness. This voice of the Gospel takes the place of the whispering murmur, which teaches the Law in specified localities. This voice, however, has no definite place and teacher. Moses whispers, but the Gospel shouts confidently and most vigorously.”
~Luther’s Works vol. 40: 8.