John 17 gives us a glimpse into Jesus’ prayer life—the Son praying to the Father for the disciples who are immediately present and for all those who would later believe.
In verse 15, Jesus prays for His disciples’ preservation. Then, in verse 17, He prays for their sanctification: “Sanctify them in the truth; your word is truth” (John 17:17). In the space of just nine words, Jesus teaches a great deal about the doctrine of sanctification. The word “sanctify” in this verse is related to the word holy. So while the text reads, “Sanctify them in the truth,” we might also say, “Make them holy in the truth.”
When a Christian asks, “What is God doing in my life?” the answer, based on Jesus’ prayer in verse 17, is simple: By the power of the Spirit and the Word, God is making us more like His Son, Jesus. That’s the work of sanctification.
Using John 17:17 as a starting point, we can define the doctrine of sanctification biblically and then establish how this work is displayed in a believer’s life.
Sanctification Defined Biblically
In the Old Testament, places, people, priests, utensils, buildings, etc., were often described as “holy.” That is, they were set apart from one use to be set apart for another. For example, a bowl used for rituals in the temple was set apart for a specific purpose in the framework of God. (See, e.g., Exodus 25:29).
When we see the word “sanctify,” we should think of it in terms of being set apart for use in the service of God. It is the process of being made less like ourselves and more like Jesus. It’s the work of renovation.
Indeed, sanctification is the fruit of being set apart in Jesus. It is distinct from justification—the act of God declaring sinners righteous on account of His Son’s finished work—but the two are closely related. While we can distinguish between justification and sanctification, we cannot divide them. The only people whom God justifies are those whom He sanctifies. Declaring us righteous, God then makes us righteous.
We might say it this way: The grace that sets us apart to God is the same grace that makes us increasingly like God.
Sanctification Displayed Progressively
Looking at the doctrine from a different angle: Sanctification is a matter of degrees. Believers can’t be more or less justified. The declaration of righteousness God makes is legal and external. But we can be more or less sanctified. Sanctification is a lifelong project.
C. S. Lewis offers a helpful metaphor in Mere Christianity:
Imagine yourself as a living house. God comes in to rebuild that house. At first, perhaps, you can understand what He is doing. He is getting the drains right and stopping the leaks in the roof and so on: you knew that those jobs needed doing and so you are not surprised. But presently he starts knocking the house about in a way that hurts abominably and does not seem to make sense. What on earth is He up to? The explanation is that He is building quite a different house from the one you thought of—throwing out a new wing here, putting on an extra floor there, running up towers, making courtyards. You thought you were going to be made into a decent little cottage: but He is building a palace. He intends to come and live in it Himself.1
In sanctification, God chisels us into the image He has intended. He cuts off useless pieces, realigns disproportionate elements, smooths out the rough edges—all with the loving purpose of greater holiness.
But as soon as we enter into that new dimension, we realize we brought with us our old fallen nature—that part of us that still loves sin. Sanctification is a kind of conflict: our old nature still clinging on, our new nature striving toward Christlikeness. The Christian is simultaneously sinner and saint, a rebellious child yet adopted into God’s family.
Sanctification is a lifelong project.
And sanctification takes time. The process is full of triumphs and trials this side of eternity. Specifically, we can look for God’s renovating work in at least three ways.
First, God sanctifies us mentally. “Do not be conformed to this world,” Paul urges the Christians in Rome, “but be transformed by the renewal of your mind” (Rom. 12:2). Our minds are constantly bombarded by input from outside of us—from podcasts, emails, videos, music, etc. Mismanaged, these influences can become hindrances to God’s work in our minds.
Second, God sanctifies us physically. From our heads to our feet—our words to our actions—it is the Father’s purpose to redeem our bodies and their works for His glory, as temples fit for the Spirit to take up residence (1 Cor. 6:19).
Finally, God intends to sanctify us totally. Paul prays for the Thessalonians along these lines: “Now may the God of peace himself sanctify you completely” (1 Thess. 5:23). We can be confident of God’s work in us when we have less and less to hide from Him—fewer doors in our hearts shut off to His rule.
Sanctification Discovered Submissively
Importantly, Jesus prays for His disciples to be sanctified “in the truth” of God’s Word. The Father uses His Word, applied in the Spirit’s power, to make us more like His Son. When we open our Bibles, we read the very words of God—the Son sent into the world from the Father to speak the Father’s words, the Son then giving His words to the apostles to preach, and the apostles, under the Spirit’s guidance, inscripturating those words for later generations.
There are two main ways we experience sanctification in the word of truth. First, we experience it personally, through activities such as daily devotions, regular Bible-reading, and Scripture memorization. J. C. Ryle comments, “Believers who neglect the Word will not grow in holiness and victory over sin.”2 Why? Because sanctification occurs “in the truth,” not apart from it.
The grace that sets us apart to God is the same grace that makes us increasingly like God.
Yet sanctification through God’s Word is not only private but corporate. The reason preaching always should be central to worship is because God has chosen the proclamation of His Word as one of the main means through which He works. We experience the sanctifying work of God in preaching in a way unlike any other. It’s perhaps for this reason the author of Hebrews exhorts the persecuted church not to forsake meeting together (Heb. 10:25)—for it’s in the meeting and listening that God sanctifies us.
At the beginning, we asked the common question “What is God doing in my life?” The answer we find in John 17:17 is as clear as it is thrilling: He is sanctifying you! The Father wills it. Jesus prays for it. The Spirit applies it. And we get to experience it.
For those of us in Christ, we are being transformed into His image, whether we can sense it or not. God is renovating the lives of those He has justified. And one day, when we see Christ, the building project will be complete. We will be just like Him (1 John 3:2).
This article was adapted from the sermon “‘Sanctify Them’” by Alistair Begg.
