I was taught by many that good preaching must be practical, focusing on action. I was even told in a couple seminary classes that every point in a sermon should be a command. I appreciate the emphasis on practicality and desiring to see people moved, changed, and empowered. But we need to be careful here. This emphasis is what often pushes the how-to, can-do, you-do sermons that amount to little more than a preaching of the law without the hope of the gospel.
How-To Preaching Leaves Us Helpless
It's easy to slip into law preaching because we want direction. We need direction. How should I pray? How do I fast? What does forgiveness look like in my life? Good preaching will answer these questions, but if all we give is how-to we leave our people with no real help or hope. The problem is how-to (law) ultimately only shows us that we-don't, and we-can't.
Let's consider prayer. Tell me that prayer is the cry of a needy soul for undeserved grace; that it is an act of worship involving praise, confession, and supplication; that in it I should reason with God according to his character and promises. Give me helpful tips. I need this. But I will continue to fail and fall in prayer even after hearing the law. So, what is my hope?
Who-Did Preaching Comforts and Compels
My hope is not that I can become better in prayer (though I need to grow in that discipline). My hope is that Jesus has faithfully and perfectly prayed for me. In Jn 17 Jesus prayed for his people, not the world. He prayed for those the father had given him, for those who would believe in his name. And he prayed that we would be kept by the power of God, sanctified by the word of God, and united as the people of God. And here is our great hope: Jesus didn't only pray for us as supplicant, but also as substitute.
Our justification means that we are forgiven of our sins (including or corrupt prayers) and that we have received the righteousness of Christ (including his perfect praying). So even when I fail in prayer, Christ's prayer not only keeps me, his prayer is counted as my own. The Father hears and receives my prayers for they have been perfect by Jesus. You see, the gospel comforts me in my failure to pray, but it also compels me to pray because I have the assurance that God hears me; that my messy prayers are beautiful to my God!
The gospel is what gives power to any practical advice we may give in a sermon. A how-to sermon is powerless without a who-did foundation.