Here’s the reality: If the sermon primarily focuses on believers, it may not connect with the visiting unbeliever. However, if it focuses primarily on unbelievers, it may not grow the believers. Finding the balance is an art, and an art very difficult to master.
In my opinion, the late Tim Keller, mastered this as well as anyone, focusing on believers and making sure unbelievers can listen in. His sermons masterfully interwove biblical commentary, apologetics, current issues, secular philosophies, cultural artifacts, and cultural needs all the while concluding in a Christ-centered fashion.
When Keller was asked, “What advice would you give to that younger you just starting out in ministry?” he replied,
It takes a long, long, long, long time and lots and lots of practice to become as good a preacher as you are gifted to be. There’s a tendency to think if you are gifted then you can just do it…Then I went and started Redeemer in New York. I thought I was as good a preacher as I was going to be. But Redeemer was a crucible for me and my preaching because these were harder people and their feedback was more negative…It took me thousands of sermons to get to the level that God had gifted me to get to.
However, as Keller noted, it will take time and lots of practice for preachers and teachers to be able to rightly divide the word of truth in a way that is both deep and wide—reaching both the believer and unbeliever.
Good preaching is worth that work.