"I therefore lay down this proposition that a sermon should always be expository. But, immediately, that leads me to say something which I regard as very important indeed in this whole matter. A sermon is not a running commentary on, or a mere exposition of, the meaning of a verse or a passage or a paragraph. I emphasize this because there are many today who have become interested in what they regard as expository preaching but who show very clearly that they do not know what is meant by expository preaching. They think that it just means making a series of comments, or a running commentary, on a paragraph or a passage or a statement. They take a passage verse by verse; and they make their comments on the first, then they go on to the next verse, and do the same with that, then the next, and so on. When they have gone through the passage in this way they imagine they have preached a sermon. But they have not; all they have done is to make a series of comments on a passage. I would suggest that far from having preached a sermon such preachers have only preached the introduction to a sermon!" Preachers and Preaching, p.72
Hear MLJ's lectures on Preachers and Preaching here.