“The chief means of grace is the preached Word. A sermon is not only an exposition of God’s Word but is itself God’s Word. It is the Son of man preaching life into the valley of dead bones, wielding the two-edged sword that kills and makes alive. It is the Holy Spirit alone who is the effectual cause of the Word’s work, but it is administered through preaching. This is why, according to historical practice, sermons begin with the invocation, “In the name of the Father, the Son, and the Holy Spirit,” and end with “Amen,” or its translation, “So be it.” The sermon is the Word of God addressed to God’s people.
Sometimes we see the sermon merely as an opportunity to make the Word effective. For some, it is an opportunity for mere reflection— data processing, to put it indelicately. For others, it is a chance to make a decision. Still others see it as a stimulation to emotional experience. But whether we make our intellect, our will, or our heart sovereign, we are exchanging the glory of God for that of the creature. As Scripture presents it, the Word itself— wielded by the heavenly agent (the Holy Spirit) and the earthly ambassador (the preacher)— does what it threatens in the law and promises in the gospel. The Word itself does this work, not because it provides an occasion for us to do something but simply by its being used by God according to his own sovereign will. It is not just the content of the Word but the preaching of the Word that is central in worship and is, strictly speaking, a means of grace.
To be sure, many other methods in our hi-tech era would appear to be more effective forms of getting us to do something. Drama can entertain and inspire, emotional choruses sung in ascending chords with growing instrumental intensity can alter consciousness and moods, while audiovisual sophistication can persuade people that the Christian message (whatever that may be) is relevant in our age. A booming anthem with a pipe organ and well-trained choir may stir us. But if the primary goal is not to get us to do something that will effect our salvation but for God to plant his Word in our heart, our criteria for effectiveness and success will be rather different. It is important for us to realize that it is not only the message of the Word but the method of preaching that God has promised to use for salvation and growth. It must, therefore, be central in worship.”
— A Better Way: Rediscovering the Drama of God-Centered Worship by Michael Horton –