Take, for example, the famous preacher Charles Spurgeon. Read Spurgeon’s sermons (I do often) and you will find he is constantly importing systematic theology into the texts he preaches on. His sermons start with a text but often become topical, engaging in systematic theology, rather than strictly expository, in keeping with biblical theology.
In fact, Spurgeon rarely truly exposited a text in any thorough or detailed way. In other words, he fails some peoples’ test of good preaching because he is certainly not expository in the modern sense of the word. Yet I agree that Spurgeon was one of the greatest preachers of all time.
Someone can effectively exposit a text on death and resurrection in 1 Thessalonians 4, say what the passage really says, and still bring in other passages that give a larger picture of the biblical doctrine of death, resurrection and Christ’s return. Someone may say “but he should have stayed only in 1 Thessalonians 4.” Well, who says? Read Peter’s sermon in Acts 3. This was a summary, a big picture of salvation, with quotes from Moses and the prophets. Or read Stephen’s sermon in Acts 7, which speaks of Abraham, Moses, David and Solomon. We can learn from the fact that they told the redemptive story (which is one reason why systematic theology must be accompanied by other forms of teaching that concern the Bible’s story-line). But these men certainly didn’t do a biblical theology of Deuteronomy or an exposition of Nehemiah, though I’m all for such things. The point is that there is not one right way to teach the Bible—the Bible can and should be taught in a variety of ways (taking into account learning styles, for instance). I’m not saying I want to see less expositional preaching and teaching. I’m all for more. But the point is that people came away from Spurgeon’s messages understanding the Bible better. This was partly because they got the big picture of how it all fits. Then when they read the Bible on their own they could better understand it. And when they read books and newspapers, they had those biblical doctrinal hooks to hang their thinking on and discern error when they saw it. It’s my opinion that people need to be taught systematic theology alongside their own Bible reading and study and the church’s exposition of various books of the Bible. It’s not either/or but both/and that will feed their minds and souls and motivate them to learn more, see accurately and live better.