The uniqueness of Luther’s theology of preaching lies in that preaching is not mere human speech about God; rather it is God’s own speech to people, which corresponds to God’s own action. God’s word acts and thus accomplishes his will, but through the agency of human speech. Preaching then is not the preacher’s discursive reflection about God and life, an exercise distinctive of the custom of the university, but is God’s audible address to sinners in need so that he might confer good on them, and clothe them with Christ’s righteousness. The preacher speaks and, in his speaking, the justifying action of God is accomplished. God creates through his opposite (i.e., the preacher) the object of his love – a people no longer under divine wrath. Preaching is not a rehashing of the old stories, nor is it a memorial speech about God’s deeds. [Gustaf] Wingren’s words elucidate Luther’s view:
[P]reaching, in so far as it is Biblical preaching, is God’s own speech to men, is very difficult to maintain in practice. Instead it is very easy to slip into the idea that preaching is only speech about God. Such a slip, once made, gradually alters the picture of God, so that he becomes the far-off deistic God who is remote from the preached word and is only spoken about as we speak about someone who is absent.
Dennis Ngien, “Luther As A Spiritual Adviser”, pages 157-158. Wingren quote from “The Living Word”, page 19.