“He will not speak on his own; he will speak only what he hears”
"Here Christ makes the Holy Spirit a Preacher. He does so to prevent one from gaping toward heaven in search of Him, as the fluttering spirits and enthusiasts do, and from divorcing Him from the oral Word or the ministry. One should know and learn that He will be in and with the Word, that it will guide us into all truth, in order that we may believe it, use it as a weapon, be preserved by it against all the lies and deception of the devil, and prevail in all trials and temptations. For there is, after all, no other way and no other means of perceiving the Holy Spirit’s consolation and power, as I have often demonstrated from Holy Writ and have often experienced myself. For I, too, am a half-baked theologian. This I say lest I exalt myself over the great minds who have long ago ascended into the clouds beyond all Scripture and have nestled under the wings of the Holy Spirit. But experience has taught me all too often that whenever the devil catches me outside Scripture and sees that my thoughts are rambling and that I, too, am fluttering toward heaven, he brings me to the point of not knowing where God is or where I am. The Holy Spirit wants this truth which He is to impress into our hearts to be so firmly fixed that reason and all one’s own thoughts and feelings are relegated to the background. He wants us to adhere solely to the Word and to regard it as the only truth. And through this Word alone He governs the Christian Church to the end.
...Earlier we heard (John 14:26; 15:26) that the Holy Spirit is sent not only by the Father but that He is also sent by, and proceeds from, the Son. Therefore this Listener must be called the Listener of both the Father and the Son, not of the Father alone or of the Son alone. Christ has stated plainly: “The Comforter, whom I shall send to you from the Father.” The expression “to send” has the very same connotation that the expression “to proceed from” has. For he who proceeds from someone is sent. Conversely, he who is sent proceeds from him who sends him. Consequently, the Holy Spirit has His divine essence not only from the Father but also from the Son, as the following words will illustrate further.
Thus these words confirm and teach exactly what we confess in our Creed, namely, that in one divine essence there are three distinct Persons: the Father, the Son, and the Holy Spirit. This is illustrated by means of a metaphor, or a picture of natural things, in order that we in our weakness may be able to know what is meant and to talk about it. But we cannot search it out or understand it. We must believe, and cling to, these words which we hear from Christ Himself, just as Christendom and especially the holy fathers and bishops did. They had disputations about this article, and they fought for and preserved it against the heretics and lying spirits who made bold to meditate on and to affect wisdom concerning these sublime, inscrutable matters beyond and apart from Scripture."
From 'Luther’s Works' (American Edition), Vol. 24: Sermons on the Gospel of St. John: Chapters 14-16. Ed. Jaroslav Pelikan, Hilton C. Oswald and Helmut T. Lehmann (Saint Louis: Concordia Publishing House, 1999).
Pic: The picture is a version of the well known icon of the Holy Trinity by Andrew Rublev (+ c. 1430). I do not subscribe to the theology of icons as set forth by the Orthodox, but this icon seems to me to be worthy of consideration for use as a pedagogical tool that illustrates the teaching of Holy Scripture. Note the pre-eminence of the Father in the setting of the figures and also the mutual acknowledgement of each Person of the other through the inclination of the head.