Recently Al Mohler has written an excellent series of articles highlighting the importance of expository preaching. In this series he seeks to encourage Evangelicals to recover the centrality of expository preaching in their churches. Here are the links to all three articles:
Expository Preaching—The Antidote to Anemic Worship -- In this article Dr. Mohler rightly concludes that "The anemia of evangelical worship—all the music and energy aside—is directly attributable to the absence of genuine expository preaching. Such preaching would confront the congregation with nothing less than the living and active word of God. That confrontation will shape the congregation as the Holy Spirit accompanies the word, opens eyes, and applies that word to human hearts."
The Sheer Weightlessness of So Many Sermons—Why Expository Preaching Matters -- In this article Dr. Mohler offers this definition of expository preaching: "Expository preaching is that mode of Christian preaching that takes as its central purpose the presentation and application of the text of the Bible. All other issues and concerns are subordinated to the central task of presenting the biblical text. As the word of God, the text of Scripture has the right to establish both the substance and the structure of the sermon. Genuine exposition takes place when the preacher sets forth the meaning and message of the biblical text and makes clear how the word of God establishes the identity and worldview of the church as the people of God."
Preaching with Authority: Three Characteristics of Expository Preaching -- In this article Dr. Mohler argues that "Authentic expository preaching is marked by three distinct characteristics: authority, reverence, and centrality. Expository preaching is authoritative because it stands upon the very authority of the Bible as the word of God. Such preaching requires and reinforces a sense of reverent expectation on the part of God’s people. Finally, expository preaching demands the central place in Christian worship and is respected as the event through which the living God speaks to his people."
I highly recommend reading this series and then returning to the Scriptures to remember again what the Lord has to say about the importance of the faithful preaching of His Word. Perhaps a good starting point would be Paul's admonition to Timothy:
NKJ 2 Timothy 4:1-5 "I charge you therefore before God and the Lord Jesus Christ, who will judge the living and the dead at His appearing and His kingdom: 2 Preach the word! Be ready in season and out of season. Convince, rebuke, exhort, with all longsuffering and teaching. 3 For the time will come when they will not endure sound doctrine, but according to their own desires, because they have itching ears, they will heap up for themselves teachers; 4 and they will turn their ears away from the truth, and be turned aside to fables. 5 But you be watchful in all things, endure afflictions, do the work of an evangelist, fulfill your ministry."