You can argue that there is nothing more important in preaching than application. Any sermon without application isn't. Sermons without application just make noise.
Ask the greats. C. H. Spurgeon claimed, "Where application begins, there the sermon begins." John Broadus wrote "The application in a sermon is not merely an appendage to the discussion, or a subordinate part of it, but the main thing to be done."1 Just as John's gospel is written for the purpose of belief and life (John 20.31), so should preaching the gospel. It's where God's word hits home.
The subject of application covers wide territory. Its about relevancy, overcoming boredom, making persuasive connections, the use of illustrations, and preaching's impact on behavior and attitude.
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The Application Spectrum
Applications can vary as to where and how they appear in a sermon, and how direct or indirect they are. Here are four different kinds:
Extended Conclusion Applications
Puritan preachers perfected a sermon style which began with exposition and ended with application. Of course, New Testament epistles are like this. Often such application is very direct (e.g. "this doctrine now means ...).
Beaded Applications
Here a sermon resembles "beads" threaded together, each of which takes the form of explanation, illustration, and application. So there may be several applications at different points through the process of exposition.
Hook Sentences
Preachers can sometimes pepper the whole sermon with 'hooks' to keep high levels of interest and application. These may be no more than a passing reference to some contemporary event, or to a familiar image. Every few sentences about Scripture are accompanied by hooks into listeners' experiences.
Application narratives
Here application occurs through a story, perhaps a retelling of a Bible story, which has its own power to influence listeners. This is likely to be indirect since it involves hearers in "making it their own story."
The Key Questions
Whichever form application takes there are two important questions lodged at its heart. They are: SW? YBH?
SW is the "so what?" of preaching. Older well behaved saints don't ask this often. They can endure much. But those not yet committed, especially younger people, particularly ask at the end of 25 minutes -- "I gave you my time. So what?" Fosdick said memorably. "Not many people, except for the preacher, come to church desperately anxious to know what happened to the Jebusites." Unapplied sermons which stick 95% in the Bible world will get shrugs. Actually, over-applied sermons which are 95% in the contemporary world risk getting a shrug from God which is worse.
For effective preaching the SW should start from the moment the Bible is opened. Nothing is more applied than a two-edged sword (Heb 4:12). As I read God's word I should ask: "Who is He, and what does He want me to be and to do? What matters for me today?"
Haddon Robinson tells about a disastrous sermon he once preached on John 14. He did his homework, but he says: "5 minutes into the sermon, I knew I was in trouble. At the 10 minute mark people were falling asleep. One man sitting near the front began to snore. Worse he didn't disturb anyone! No one was listening. Even today, whenever I talk about that morning, I still get an awful feeling in the pit of my stomach."