Tim Keller in his book The Prodigal God: Recovering the Heart of the Christian Faith (Riverhead Books, 2008, pgs. 129-130):

We habitually and instinctively look to other things besides God and his grace as our justification, hope, significance, and security. We believe the gospel at one level, but at deeper levels we do not. Human approval, professional success, power and influence, family and clan identity—all of these things serve as our heart’s ‘functional trust’ rather than what Christ has done, and as a result we continue to be driven to a great degree by fear, anger, and a lack of self-control. You cannot change such things through mere will-power, through learning Biblical principles and trying to carry them out. We can only change permanently as we take the gospel more deeply into our understanding and into our hearts. We must feed on the gospel, as it were, digesting it and making it part of ourselves. That is how we grow.

The end of teaching and preaching cannot be biblical principles from the text. We must make connections with the Gospel with every text from which we teach. If all we do is teach biblical principles from a text (even if they’re all true) and do not connect the text to the Gospel, then we are implicitly telling our audience: “the key is to now go and do what I just taught you.” If our audience wasn’t reminded that it’s through the Gospel of grace that God empowers us to obey His Word, then likely many will try to obey out of sheer will-power. This kind of response would be the opposite of what we should encourage in people. Obeying out of will-power will neither lead to actually doing what the text requires nor to pleasing God.

As we prepare to teach Scripture to others, we must remember this about our audience (to slightly alter Keller’s words):

They cannot change [whatever the text says or implies they should] through mere will-power, through learning Biblical principles and trying to carry them out. They can only change permanently as they take the gospel more deeply into their understanding and into their hearts. They must feed on the gospel, as it were, digesting it and making it part of their selves. That is how they grow.

As I reflect on the various opportunities over the years that God has graciously given me to teach God’s Word to others, I am deeply convicted by these words. I realize that much of my teaching has been just about biblical principles. Don’t get me wrong—that’s good on one level. Without trying to be prideful, I do believe I can say that I have taught a lot of truthful principles from Scripture (although I haven’t been without error). But, many of my messages were not clearly connected to the gospel. If I dare be honest, probably even most of my messages lacked gospel-centrality. Sure, I often talked about how to get saved—through repentance and faith in Christ. But, for the Christians who were present, my message for them was largely a challenge to live a certain way.

My great failing has been that I didn’t connect those challenges with the Gospel. I didn’t explain how they could obey. I merely explained that they should obey. I doubt that many listeners left the meeting thinking deeply about how God would empower them through His grace to follow His Word. Rather, if any thought about the implications of my message for their lives, their thoughts would have been along the lines of “how will I ever do what the Bible says I must?” with perhaps accompanying guilt when realizing that they couldn’t or haven’t.

One of my great hopes for going to seminary is to learn how the Gospel is at the forefront throughout all the Scriptures, and to be equipped to effectively teach and preach Scripture to others in this faithfully gospel-centered way. I cannot undue my mistakes in the past. Only God in His sheer mercy can redeem what others have heard from me that was not saturated with His Gospel of grace. From here on forward, I want any future speaking opportunities (should God graciously grant me some) to be saturated with God’s Gospel of grace. May God empower me through His grace to do so. After all, I can’t do this by sheer will-power. And I’m so thankful that despite all my failings, by His doing I rest in His grace and unchanging love for me.