Looking straight at a light bulb isn’t the “brightest” thing to do (pun intended). You feel a shot of pain at the back of your eye and you see pretty colors for the next five minutes, but it leaves you with no lasting damage. Looking at a laser, on the other hand, could blind you.
The power of lasers makes them useful for everything from scanning groceries, to correcting vision, to cutting diamonds and even (my personal favorite) to annoy cats.
According to a super-technical, highly complex website from NASA (that was, ahem, designed to teach science to children), the difference between lasers and light bulbs has everything to do with the wavelength of the light waves they each emit.
The first picture illustrates the light waves emitted by a light bulb, while the second illustrates those emitted by a laser. Light bulbs emit many different wavelengths, while lasers emit just one.
Here is my simple, non-astrophysicist hypothesis: Lasers are more powerful than light bulbs because they are more specific with the wavelengths they emit. I am convinced that your prayers for preaching also become more powerful the more specific they are.
A lesson from lasers on powerful prayer
You know the importance of praying for your sermon—or at least you should, because prayer-less preaching is powerless preaching. But, even though you believe this, my guess is that you sometimes try to “pray yourself hot,” but barely manage to “pray yourself lukewarm.” I know I do. I believe we can learn from the laser when it comes to praying ourselves hot.
Powerful prayer is about aligning our prayers with God’s own purposes for His Word. It is not about hitting a magical combination of words and posture, as if God were some divine vending machine that dispenses power when we press the right buttons. God intends to accomplish His purposes through His Word. He intends to do something. And the more specifically you align your prayers with God’s purposes for your preaching text, the more powerful your prayers will become. In fact, I am convinced the most powerful prayer for preaching happens when we align our prayers with God’s specific purpose for the preaching text.
In the exegetical process, your goal is to discern God’s original purpose for the text. It is a journey from general to specific. When you have discerned the specific purpose, you will have what you need to pray in line with God’s heart for the text. But you don’t have to wait until the end of the exegetical process to pray God’s purpose, nor should you!
The “Purpose Funnel”
You can pray God’s purpose throughout the whole preparation process by allowing the process to carry you into an increasingly specific prayer. This process looks like a funnel with three levels:
Level 1: Know God’s General Purpose for Your Preaching Text
You know God’s general purpose for every text you will ever preach. Before you parse a verb, diagram a sentence or read a commentary, you know that God desires to bring Himself glory through the passage. The Bible accomplishes this purpose when people are transformed by the Word and respond by living lives of worshipful obedience. Your general purpose will always be God’s glory through changed lives. Before you dive into the rigors of preparation, you can pray this purpose, confident that it aligns with God’s heart for the text.
Level 2: Identify the Category of Purpose
Based on 1 Timothy 3:16, Murray Capill identifies the four “main purposes” for God’s Word as teaching/rebuking, training/correcting, testing/convicting and encouraging/exhorting. Jay Adams describes the three broad categories of purpose in Scripture as “to inform, convince or motivate.” For instance, the purpose of the “Christ hymn” in Philippians 2:6-11 is to teach the doctrine of Christ’s humiliation and exaltation, but it flows directly from Paul’s exhortation to unity that begins in 1:27. So, the Holy Spirit inspired this passage both to teach and to motivate.
Level 3: Articulate the Specific Purpose
At the end of your exegetical process, you should be able to articulate God’s specific purpose for your preaching text. For Philippians 1:27-2:11, it may sound something like: “Paul wanted to teach the Philippians about Christ’s humiliation and exaltation in order to motivate them to be unified.” In order to be faithful to the text, your sermon’s purpose will closely reflect this original purpose. For this passage, you might say, “I want my hearers to understand the doctrine of Christ’s humiliation and exaltation so they will be unified.”
Light bulbs to laser beams
As you work through the preparation process and press more deeply into this “purpose funnel,” you are able to progressively increase the specificity of your prayer. At levels 1 and 2, you pray like a light bulb. When you pray God’s general purpose for the passage and the broad categories of purpose, your petitions combine like the varied wavelengths of a light bulb to produce a warm glow. These prayers are good and they are powerful, because they align with what God generally desires to do through this text. Nobody ever said a light bulb was a bad thing.
You should never neglect to pray God’s general purposes for the text. However, if you only pray in a general way, your prayers will lack the power that specificity brings. Light bulbs are good and they are important; lasers beams are simply more powerful.
At level 3, you pray like a laser beam. When you pray God’s specific purpose, it is like switching from many wavelengths of light to one. As the specificity of your prayers increase, the temperature of your prayers will increase as well. The best way to “pray yourself hot” is to start with light bulb warmth and allow the text itself to gradually raise the temperature of your prayers to laser beam hot. As you faithfully exegete the text and discern God’s purpose, the temperature of your prayers increases.
The Benefits of laser beam prayers
From my personal experience, I have seen at least three benefits of praying the purpose funnel. First, the quantity of my time in prayer has increased. Honestly, I think this is due to the simple fact that it is easier to get distracted praying generalities than specifics.
Second, I know how to better support God’s purpose for the text. Make no mistakes, God does the work of transformation. But he also calls us to participate. As preachers, we need to call people to respond in specific ways, and we need to support that response. When you spend time praying God’s specific purpose, you will often emerge with tangible, specific ways to support this purpose.
Third, my prayers simply feel more powerful. I realize that this is not a quantifiable benefit, but it’s real nonetheless. I have shed more tears, shouted more petitions and pleaded more earnestly for God to work in my hearers’ lives. I believe this effect is simply the result of bringing my prayers into closer alignment with God’s heart for the text.
So, preacher, when it comes time to “pray yourself hot,” start with a light bulb but finish with a laser beam.
 Murray Capill, The Heart is the Target: Preaching Practical Application from Every Text (Philipsburg, NJ: P&R, 2014), 63.
 Jay E. Adams, Pulpit Speech (Grand Rapids, MI: Baker, 1971), 14.