Among the four or five dialogues I had with J. Ligon Duncan at the Pastor’s Conference, one of them was extremely significant. Earlier Dr. Duncan spoke on Expository Preaching from the Old Testament. It was certainly a pertinent topic in light of the almost overwhelming Baptist audience, who tend to overlook the relevance of the Older Covenant. He listed ways to preach the Old Testament. His last point is the one I wish to bring to our attention: Preach the Christian Life in the Old Testament. As an example of this, Ligon reminded the audience of Luke 17 where the author urges the reader to “Remember Lot’s wife”. In that example, she is used not merely as a Redemptive Historical figure, but as a physical representation of how we ought not to behave. In Duncan’s words, those who avoid using the Bible in order to affect our behavior are denying the very writers of Holy Writ. Simply because there have been abuses in preaching–which leads to legalism and moralism– does not mean that we ought not to stress it where it is stressed in the text.
John Frame’s criticism of this form of thinking is worth reading:
I have heard Christians say that our goal in preaching should be only to spread the word, not to bring conversion, since that is God’s work. The result is often a kind of preaching that covers biblical content, but unbiblically fails to plead with sinners to repent and believe. 
It is here where Frame’s language is helpful. He divides the Bible into two emphases: Indicative and Imperative. The “Indicative” refers to what happens in redemptive history (Salvation’s history or the unfolding of the ages), whereas the “Imperative” refers to the obligation or responsibility of the Christian under God’s authority. When the Bible is preached and does not challenge in any way our behavior, we are disobeying apostolic instruction. Further, the opposite is also dangerous. When the preaching is merely concerned about changing behavior, the message becomes moralistic and meritorious in nature. The Scriptures bring these two together in an unending bond. Paul himself brought both together in Colossians 3:1-3: You have been raised (Indicative)…so set your hearts on things above (Imperative). The Scriptures demand both.
 Luke 17:32
 In this case, we ought not to disobey God’s Word. There is a strong ethical component here, not an abstract mention.
 Frame, John. The Doctrine of God, Footnote, pg. 123.