It is a temptation that we all face at one time or another. We have a passage to preach and there is something in the passage that moves our mind somewhere else in the canon. Perhaps a term, a theological issue, a familiar concept. Then we are tempted to preach the other text using this one. I remember taking a distance learning course once on the Pastoral Epistles, but the lecturer obviously would have preferred to be in Romans as he kept going back there!
I was just listening to Walter Kaiser teaching on Genesis 4. He pointed out how we so readily want to read in a Leviticus 17 focus (“blood sacrifice”) while the text of Genesis 4 places the emphasis not on the sacrifice type, but on the state of the man as he offered what he offered (“first fruits” being significant on the part of Abel). My goal here is not to teach Genesis 4, I’ll leave you to sort out tradition from exegesis on that passage. My point is that we must always try to preach the passage we have before us, rather than reading in a concept that would be better taught in a passage that really teaches it.
The Bible has so much in it, but that doesn’t mean we can preach anything from any passage . . . or even multiple things from any passage. Let’s be sure to preach the Word!