Not all proclamation is real proclamation. Proclamation (church preaching and sacrament) cannot ever claim to "be" the Word of God. It cannot contain the Word of God, hold it, grasp it, claim it as its own. No, according to Barth, "Proclamation must ever and again become proclamation." (CD I.1 §4.1 p. 88).
How does proclamation "become" the Word of God. Barth gives four factors, which he calls concentric spheres.
1) In the outermost sphere, the Word of God is a "given commission." The givenness is important here. This is not a human word. It is given from God and cannot be created through human means, through human motivations. God's word remains free.
2) God's Word is the theme of proclamation. God's word cannot be reduced to objects of human perception, either external perception (the five senses) or internal perception (thought, perception of the mind).
3) Proclamation is judged not by human standards of judgment, but by the Word of God itself. God's Word judges whether proclamation is or is not the Word of God. Human judgments must be made about proclamation, but they are not decisive.
4) Finally, the Word of God is an event in which God acts. As Barth writes, "proclamation becomes real as God commands, God comes on the scene, God judges." (CD I.1 §4.1 p. 93).
What I found most interesting in this section is the close intertwining of the human and the divine. When God's Word comes, when God decides to act, it is through human means. God does not come and subsume the human factors. God comes through the human factors. God comes through humanity, with all of its weakness, all of its frailty, all of its imperfections, nevertheless God comes and redeems, makes the human all that it should be.
Let's end with the words of Barth himself:
"The miracle of real proclamation does not consist in the fact that the willing and doing of proclaiming man with all its conditioning and in all its problems is set aside, that in some way a disappearance takes place and a gap arises in the reality of nature, and that in some way there steps into this gap naked divine reality scarcely concealed by a mere remaining appearance of human reality... As Christ became true man and remains true man to all eternity, real proclamation becomes an event on the level of all other human events." (CD I.1 §4.1 p. 94).