Martin Luther put it this way:
“Thus when you hear a sermon by St. Paul or by me, you hear God the Father Himself. And yet you do not become my pupil but the Father’s, for it is not I who is speaking; it is the Father. Nor am I your schoolmaster; but we both, you and I, have one Schoolmaster and Teacher, the Father, who instructs us. We both, pastor and listener, are only pupils; there is only this difference, that God is speaking to you through me. That is the glorious power of the divine Word, through which God Himself deals with us and speaks to us, and in which we hear God Himself.” 
 Martin Luther, Sermons on the Gospel of St. John, trans. Jaroslav Pelikan, “Luther’s Works,” (Concordia/Fortress Press, 1968), vol. 23, 97-98.