The good news is that the Spirit of God is involved in every aspect of the communication loop. As Fred Rogers, famous as "Mr. Rogers," is reported to have said: "The space between my mouth and your ears is the land of the Holy Spirit." And it is in that out-of-our-reach feedback loop that we stand when we stand before other human beings and speak the Word. (See Acts 10:42; 14:3; Hebrews 2:3-4.)
And, as already hinted at, the Spirit is at work quite apart from anything we are doing. This is the real wonder of the mystery in which we stand. In John 15:26, Jesus says of the Paraclete, "He will bear witness about Me" (ESV). I had for years taken this to mean that he will help us bear witness, that as we seek to speak of Jesus in the world, the Spirit will be present to help us. And he does. But that is not what Jesus is speaking about in the promise of John 15:26. It was Lesslie Newbigin who, in his brilliant theological commentary on the Gospel of John, written while serving in India, helped me see what Jesus is saying; and it changed the way I understood the preaching moment (Lesslie Newbigin, The Light Has Come: An Exposition of the Fourth Gospel [Grand Rapids, MI: Eerdmans, 1982]), p. 206). We are not the primary actors in the event.
"It is important to note what is not said," Newbigin begins (ibid). "It is not said that the Spirit will help the disciples to bear witness. That would make the action of the disciples primary and that of the Spirit auxiliary. What is said is that the Spirit will bear witness and that--secondarily--the disciples are witnesses" (ibid). Newbigin goes on to remind us that it is not the work of humans to bring other humans to acknowledge Jesus as he really is; it is always the work of God (Jn. 6:44--the Father 'draws' us to Jesus). Then Newbigin writes this:
What is promised here is that the Spirit will perform His own miracle in the hearts and consciences of people so that they are brought to recognize Jesus as the one he is. The words, the works and--above all--the suffering of the community will be the means by which the witness is borne, but the actual agent will be the Spirit who, because he is the Spirit of the Father, is the Spirit of truth. When the Lord says to Israel, "You are my witnesses" (Isa. 43:10), there is no suggestion that this is a summons to proclamation. Israel is the witness to the majesty and glory of the Lord, not on account of anything that Israel says or does, but on account of those mighty works of which the Lord is the subject and Israel is the object. It is in this sense that the disciples will be witnesses.... Their life, their words, their deeds, their sufferings will thus be the occasion, the place, where the mighty Spirit bears his own witness in the hearts and consciences of men and women so that they are brought to look again at the hated, rejected, humiliated, crucified man and confess: "Jesus is Lord." It is the Spirit who is sovereign. The promise to the community of the disciples is not that they will have the Spirit at their disposal to help them in their work of proclamation. That misunderstanding has profoundly distorted the missionary action of the Church and provided the occasion for a kind of missionary triumphalism of which we are right to be ashamed. The Spirit is not the Church's auxiliary. The promise made here is not to the Church which is powerful and "successful" in a worldly sense. It is made to the Church which shares the tribulation and the humiliation of Jesus, the tribulation which arises from faithfulness to the truth in the world which is dominated by the lie. The promise is that, exactly in this tribulation and humiliation, the mighty Spirit of God will bear his own witness to the crucified Jesus as Lord and Giver of life (ibid, 207-8).That is the mystery. That is the space into which we enter when we stand up before other human beings (some eager, some weary, some afraid, some hostile) and, Bible in hand, try to faithfully say what God is saying in a text.