From the opening page of the opening chapter, “The Glory of Preaching: A Historical Sketch”:
Preaching is indispensable to Christianity. Without preaching a necessary part of its authenticity has been lost. For Christianity is, in its very essence, a religion of the Word of God. No attempt to understand Christianity can succeed which overlooks or denies the truth that the living God has taken initiative to reveal himself savingly to fallen humanity; or that his self-revelation has been given by the most straightforward means of communication known to us, namely by a word and words; or that he calls upon those who have heard his Word to speak it to others.
First, God spoke through the prophets, interpreting to them the significance of his actions in the history of Israel, and simultaneously instructing them to convey his message to his people either by speech or by writing or both. Next, and supremely, he spoke in his Son, his ‘Word…made flesh’, and in his Word’s words, whether spoken directly or through his apostles. Thirdly, he speaks through his Spirit, who himself bears witness to Christ and to Scripture, and makes both living to the people of God today. This Trinitarian statement of a speaking Father, Son and Holy Spirit, and so of a Word of God that is scriptural, incarnate and contemporary, is fundamental to the Christian religion. And it is God’s speech which makes our speech necessary. We must speak what he has spoken. Hence the paramount obligation to preach.
John Stott, Between Two Worlds, p. 15.