It is so important to understand the text before you preach it! I don’t mean just knowing what the big words mean. I don’t mean just having a collection of exegetical insights to share. I don’t mean even having a sermon vaguely based on certain parts of the text. I mean really understanding what the text is saying – understanding it’s unity, it’s message, it’s point, it’s purpose, it’s role in the broader flow of thought in the book. What if you’re not ready though?
Suggestion with several caveats to follow: If you’re not ready, don’t preach it. Instead preach an old message again that you are confident is biblically sound.
Just think what an example that might be for the congregation! “We were scheduled to be in Epistle XYZ 4:15-22, but I’ve been studying it over several weeks and still am not there yet – some passages take real work to really grasp! So I’ll keep on studying, but for today, let’s look again at . . . ”
Caveats a coming!
1. Chances are, they won’t remember a message you re-preach. But it would be honest to tell them it’s worth a second look at this old message rather than trying to “slip it through.”
2. Recognize that as a Bible student we never fully plumb the depths of any passage and as a preacher we shouldn’t really present all the plumbs either! It takes wisdom to know the difference between “I’ll never fully plumb this passage” and “I haven’t grasped the fundamental unity and flow of thought in this passage.
3. It is in no way a good example if you simply started too late.
4. Whether you are a paid pastor preaching weekly, or an unpaid preacher preaching periodically, there is an element of commitment involved. It will undermine your credibility if you follow the above suggestion more than very rarely! (In fact, if you are only doing one section in a series from the same book, you can’t simply make the subsequent weeks shift by missing your section. Get help earlier in the process and make sure you grasp the passage before you preach it, for surely you must preach it!)
5. It is probably better to take this post as a strong prod to really be prepared, rather than actually trying what I suggest! (I’d be interested to hear if anyone has ever publically announced their need for more time to study a certain passage!)
Biblical Preaching 
I have told the congregation that the message I was working on would not “come together” for me and therefore they were about to hear a message they have heard before. I have done this more than once, but I preach to a very small congregation of folk who are very gracious and forgiving.
Peter:
I have told people that I was not ready more than once. And when I explained WHY I was not ready (sometimes it was the text, a few times it was events that they totally understood), I uniformly received comments of appreciation. It showed that I valued both the Word as well as their time. I think it actually enhanced in their mind the importance of the preparation that I have done. (And yes, they hardly ever remember the sermon that I repeated. That is one of God’s ways of keeping me humble).
Several years ago when I was preaching through Hebrews, I confessed on several occasions that even though this was one of the great books of the New Testament I wasn’t sure that I had truly gotten my arms around it.
I do think people appreciate knowing that even their pastor has difficulties with certain texts.
I do this rather often. Last Sunday in the Bible class, I repeated the same lesson, this time with an outline. They had no clue, and I told them this was a repeat.
My sermons seem to be a repeat anyway. What’s up with this.
I tell people, Ha I am learning this passage, I will get back with you next week.
Great stuff Peter.
I am going to sent this to my Asso.