I think it may be possible to say that every sermon should have three aspects or purposes. First, you need to preach the text in its Scriptural context; second, you need to preach Christ and the gospel every time; and finally, you need to preach to the heart. Put another way, you should preach the truth, not just your opinion; you should preach the good news, not just good advice; and you should preach to make the truth real to the heart, not just clear to the mind.
Taken from Preaching to the Collective Heart, by Tim Keller.
