THE HOW OF HOLINESS

Most Christians I know want to be holy. They genuinely do. They read the Bible, they pray, they show up on Sunday, they take their sin seriously. But when it comes to actually growing — actually changing — they aren't sure what to do next.

They know grace is free. They've heard it preached. They believe it. But they also know they shouldn't just sit on the couch waiting for God to zap them into holiness. So what are they supposed to do?

It’s a great question. And it’s an old one.

Paul got the same pushback. By the time he finished preaching free grace in Romans 1 through 5, someone raised their hand: “Shall we go on sinning so that grace may increase?” (Romans 6:1). His answer was not to dial back the grace. It was “By no means!”—about as forceful as Greek gets—and then he did something surprising. He didn’t hand them a to-do list. He pointed them to an identity. You died. You were buried with Christ. You rose. Who you are has changed. Now live from that reality.

That’s union with Christ. And it changes everything about how we pursue holiness.

Walter Marshall was a Puritan pastor in England in the 1600s who spent years struggling with this exact tension. He went to Richard Baxter for help and came away more burdened, not less. It wasn’t until a conversation with Thomas Goodwin—who told him his greatest sin was failing to believe on Christ for the sanctifying of his nature—that the lights came on. He spent the rest of his ministry unpacking what Scripture teaches about how believers actually grow in holiness. His book, The Gospel Mystery of Sanctification, has been called by some the most important book on sanctification ever written. 

Marshall’s argument, built from fourteen directions drawn entirely from Scripture, comes down to this: holiness flows from union with Christ, received by faith. Not from willpower. Not from self-improvement. Not from pulling yourself up by your bootstraps. From Christ in you.

If you want to understand the whole book, the arc is simple. We need more than knowledge of God’s law to obey it—we need new hearts, new strength, new life. And all of that comes through being united to Christ by faith (Chapters 1–4). We cannot produce holiness from our natural state, no matter how hard we try (Chapters 5–8). And the comforts of the gospel—assurance, the love of God, the certainty of our adoption—must come before our obedience, not as a reward for it (Chapters 9–11).

But it’s the final three chapters, or as he calls them directions, where Marshall gets the most practical. And they speak directly to the question we began asking.

Direction 12 is what Marshall calls the principal direction of the whole book. He says there is a “rare and excellent art of godliness” that most Christians have never been taught.

Here’s the art: stop trying to live the Christian life from your old nature and start living it from your new one.

Scripture describes two realities at work in every believer. The old man—the flesh, what we inherited from Adam—is described by Paul in Romans 8:7 as hostile to God’s law, unable to submit to it. The new man—what we receive by being united to Christ through faith—is described in Galatians 2:20: “I have been crucified with Christ. It is no longer I who live, but Christ who lives in me.”

Most of us, when we want to grow in holiness, default to working on the old nature. We make resolutions. We grit our teeth. We try to tame the flesh through sheer determination. Marshall’s point—and it’s Paul’s point before him—is that the flesh was never designed to produce holiness. Christ did not die so that the old man could be reformed. He died so that it could be crucified (Romans 6:6), and so that we could live by a power that is not our own.

The art of godliness is learning to draw from the new nature by faith, rather than white-knuckling the old one into compliance.

But Marshall anticipates our original concern. If it’s all about faith, does that mean we stop reading the Bible? Stop praying? Stop taking the Lord’s Supper? Stop gathering with the church?

Absolutely not. That’s Direction 13.

Marshall insists that the means of grace—the Word, prayer, the sacraments, meditation, fellowship—are not set aside by faith. They are established by it. But they must be used rightly. They are, in Marshall’s phrase, “helps to the life of faith” and “instruments subservient to faith.” They point you to Christ. They strengthen your hold on him. They nourish the new nature.

The danger is turning them into something else. You can read the Bible legalistically. You can pray as a way of earning God’s favor rather than receiving it. 

Marshall puts it plainly: we must beware of using the means of grace “in opposition rather than in subordination” to the way of salvation by free grace through faith. God’s ordinances, he says, are like the cherubim of glory: made with their faces looking toward the mercy seat. They are made to guide us to Christ.

And then Direction 14 does something unexpected. It encourages.

Marshall says this way of life—walking by faith in union with Christ—is not only the right way. It is the freest, most pleasant, most peaceful way to live. He grounds this in Scripture after Scripture: “The ways of wisdom are ways of pleasantness, and all her paths are peace” (Proverbs 3:17). “They who wait upon the Lord shall renew their strength” (Isaiah 40:31). Christ’s burden is light because his Spirit bears it with us (Matthew 11:30).

And Marshall names the alternative with precision. “The doubts of salvation that people meet with,” he writes, “arise from putting some condition of works between Christ and themselves.” That is the exhaustion. That is the fear that never quite lifts.

But walking by faith is free from that. Free from slavish fear. Free from the endless self-assessment of whether you’ve done enough. Not because effort doesn’t matter—it does. But because the effort flows from someone who is already held, already loved, already united to Christ.

So if you’re someone who wants to be holy and doesn’t know how to get there—you’re in good company. Read the Word. Pray. Gather with the saints. Take the bread and the cup. But do all of it with your eyes on Christ, not on your performance. 

Marshall closes his whole book with a single sentence worth memorizing:

“Sanctification in Christ is glorification begun, as glorification is sanctification perfected.”

In Christ you are already becoming what you will one day fully be.