May the God of peace himself sanctify you wholly; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ. He who called you is faithful, and he will do it.

Introduction: The Necessity of Holy Living

How can you have the assurance of salvation if holiness is necessary?

Vast portions of the Christian church today in America seek assurance by making holiness of life unnecessary. If holiness of life is not necessary to get to heaven, then an unholy person can have assurance that he will get there. They don't just deny that perfection is not required for entering heaven (which is true; we do not attain practical perfection in this life); but they go beyond that and say that no degree of obedience or holiness or purity or goodness or love or repentance or transformation is required for entering heaven. They say that if God required any measure of practical obedience or holiness, it would do three terrible things: 1) nullify grace and 2) contradict justification by faith alone and 3) destroy assurance.

But that is not true. The Bible teaches that none of those things happen when the biblical necessity for holy living is rightly understood. There is a glorious assurance in the Christian life! But it is not found by denying the demand for holiness.

1. Does Not Nullify Grace

The necessity of holy living does not nullify grace.

It is based squarely on the pardon of grace. And it demonstrates the power of grace. In 1 Corinthians 15:10 Paul said, "By the grace of God I am what I am, and his grace toward me was not in vain but I worked harder than any of them. Nevertheless it was not I but the grace of God which is with me." Grace is not only the pardon that passes over our badness; it is also the power that produces our goodness. If God says that it's necessary for grace to do that, it is not a nullifying of grace when we agree with him.

2. Does Not Contradict Justification by Faith Alone

The necessity of holy living does not contradict justification by faith alone.

Three weeks ago I tried to show that all the sins of God's people, past, present, and future, are forgiven because of the death of Christ once for all. I said that this justification on the basis of Christ's death for us is the foundation of sanctification—not the other way around. I put it like this: the only sin we can fight against successfully is a forgiven sin. Without a once-for-all justification through Christ, the only thing that our striving for holiness produces is despair or self-righteousness.

But I did not say that the work of God in justification makes the work of God in sanctification optional. I didn't say (the Bible doesn't say) that forgiveness makes holiness optional. It doesn't make it optional, it makes it possible. What we will see today is that the God who justifies also sanctifies. The faith that justifies also satisfies—it satisfies the human heart and frees it from the deceptive satisfactions of sin. Faith is the expulsive power of a new affection (Thomas Chalmers). That is why justification and the process of sanctification always go together. They both come from the same faith. Perfection comes at the end of life when we die or when Christ returns, but the pursuit of holy living begins with the first mustard seed of faith. That's the nature of saving faith. It finds satisfaction in Christ and so is weaned away from the satisfactions of sin.

3. Does Not Destroy Assurance

The necessity of holy living does not destroy assurance.

The human mind might reason like this: if some measure of holy living is required and if it cannot be precisely quantified—if you can't tell me exactly how much is necessary—then that requirement will always leave me unsure if I have enough. So any requirement for holiness or obedience at all destroys assurance.

But this is simply not the reasoning of the Bible. The Bible shows abundantly that there is a "holiness without which we will not see the Lord" and we are told in Hebrews 12:14 to "pursue" it. But it does not imply that this destroys assurance. And the reason it doesn't is what today's sermon is about. Namely, God's commitment to sanctify us—to make us as holy as we need to be in this life—is as sure as his election and his predestination and his justification and his call. What gives us assurance in this matter is not primarily focusing on the measure of our holiness, but on the measure of God's faithfulness to do the sanctifying work he promises to do. There's the key.

Exposition: God's Commitment to Sanctify Us

So let's look at this in our text. Notice three things: the commandments, the prayer, and the promise.

1. The Commandments

Paul has just finished giving a string of commandments in verses 14–22 which comes to an end in verse 22, "Abstain from every form of evil." So we know that God uses commandments and incentives in the way he sanctifies us. He does not say: "I am the one who sanctifies you, so I have nothing to tell you to do." The way he sanctifies is not merely subconscious. He deals with our minds and our motives. That's the first thing to notice.

2. The Prayer

Then in verse 23 Paul shifts from exhorting or commanding us to be holy to asking God to make us holy: "May the God of peace himself sanctify you wholly; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ." So not only does God use commands and incentives in the way he makes us holy, he also uses the prayers of his people. He not only deals with your mind and motives in the way he makes you holy; he deals with the minds and motives of others so that they pray for you.

3. The Promise

Notice not only the commandments and the prayer, but most important the promise of God. After commanding us to pursue holy living in verses 14–22 and praying that God would sanctify us in verse 23, Paul says the decisive thing in verse 24: "He who called you is faithful, and he will do it."

This is the way Paul handles the assurance problem. Let it shape your thinking this morning. It is mere human reasoning and not God that says: "Well, he is commanding us to abstain from evil, so it must be up to us to get holy, and therefore it's not assured." It is mere human reasoning and not God that says: "Well, he is praying for God to sanctify me, so it depends on Paul's prayer and God may or may not answer, and so it is not assured." All that is wrong thinking. It's not what the text says. Right thinking moves on to verse 24 and says: God's faithfulness combined with God's call proves he WILL do it! "He who calls you is faithful, and he WILL do it." What's the IT? The "it" is what Paul's been commanding and what he's been praying for, namely, sanctification. God will do it.

That is the foundation for full assurance. Paul did not say that you have to make holy living unnecessary to have assurance. He said that God is faithful and he WILL do it. The issue of assurance is: will we trust him not only for the grace to forgive our sins, but also for the grace to make headway in overcoming our sins? Will we believe what verse 24 says: "God is faithful; he will do it"?

When Will God Do It? 

Now if you are looking at verse 23 carefully, you may have the question I had: When Paul prays that God would sanctify us and keep us blameless "at the coming of our Lord Jesus Christ," does he mean that God will change us then in the twinkling of an eye when Jesus comes, or does he mean that he will work in us now so that we will be holy when Jesus comes? Are verses 23 and 24 a prayer and a promise for what God will do all at once only when Jesus comes? Or are they a prayer and a promise for what God will do now in the lives of believers to prepare them for that day in holiness?

My answer is that it's a prayer and a promise for God to do what needs to be done now. My reason for this is not only that sanctification usually refers to the process of becoming holy now, but also the parallel in chapter 3:12–13 shows that this is what Paul means.

May the Lord make you increase and abound in love to one another and to all men, as we do to you; so that he may establish your hearts unblamable in holiness [that's what Paul prays for in 5:23] before God our Father at the coming of our Lord Jesus Christ [same phrase as in 5:23] with all his saints.

So what Paul is praying is that God would do something NOW, namely, make us increase and abound in love. And the goal of this progressive work in us NOW is that when the end comes, we might be established before God in holiness, because love is the essence of human holiness.

So my conclusion is that 1 Thessalonians 5:23–24 really does teach that God is the one who sanctifies NOW. He does it through commandments and incentives that appeal to our minds and our motives. He does it through prayer. But however he does it, and however slowly it comes, and however imperfect we feel, the main thing is that GOD does it, and he WILL do it. That is the ground of our assurance. "He who calls you is faithful. He will do it." Assurance does not come from making holiness optional. It comes from knowing God is faithful.

Why God's Call Guarantees His Sanctifying Work 

But why is it that the faithfulness of God commits him to sanctify us? The key is the connection between the other parts of our salvation and God's work of sanctification. You can see this clearly in verse 24. Paul says, "He who calls you is faithful. He will do it." It's as if Paul said, "He called you! Don't you see? He called you! And if he called you, then he WILL sanctify you. That's what his faithfulness means. Don't you get it?"

And you scratch your head and say, "Why does the fact that he called us mean that he has to sanctify us?" And Paul says, "It's because his purpose in calling you was that you might become holy. Holiness is the invincible purpose of God in your call. He would be unfaithful to his purpose if he just called and didn't sanctify. That's what I said back in 4:7, "God has not called you for uncleanness, but in holiness." "God called you with a holy calling" (2 Timothy 1:9). His purpose in calling you is your holiness. He will do it. He's faithful.

I hope you begin to feel what this means for the foundations of your assurance. It means that every successive step of your salvation is rooted in the certainty of all the steps that have gone before. Your sanctification is rooted in your call and guaranteed by your call. Your call is rooted in the death of Christ for sinners. The death of Christ is rooted in predestination and predestination is rooted in election. Once you feel yourself caught up in this great, objective, God-wrought salvation, you know yourself loved with an omnipotent, everlasting, electing, predestining, atoning, calling, sanctifying, saving love. And you sing, "God is faithful. He will do it!"

God's Sure Purpose for Your Holiness 

But not only that, the aim of God in your election was your holiness. Ephesians 1:4, "God chose us in him before the foundation of the world that we might be holy and blameless before him in love" (cf. 2 Thessalonians 2:13). Your holiness is as sure as your election.

Not only that, the aim of God in your predestination was your holiness. Romans 8:29, "Those whom he foreknew he predestined to be conformed to the image of his Son." Becoming like Jesus is as sure as God's purpose of predestination.

Not only that, the aim of God in the death of his Son was your holiness. Ephesians 5:26, "Christ loved the church and gave himself up for her that he might sanctify her"—make her holy. Your becoming holy is as sure as God's invincible purpose in the death of his Son.

In choosing you his purpose was your holiness. In predestining you his purpose was your holiness. In dying for you his purpose was your holiness. In calling you his purpose was your holiness. And so we can say with Paul in verse 24 not only, "He who called you is faithful, he will do it—he will sanctify you," but also, "He who chose you is faithful, he will do it. He who predestined you is faithful, he will do it. He who sent his Son to die for you is faithful, he will do it.

2 Thessalonians 2:13 says, "God chose you from the beginning to be saved through sanctification"—not apart from sanctification. Salvation comes through sanctification, and no other way (cf. Romans 6:22). We have a great and glorious ground of assurance not because holiness is superfluous, but because God is faithful. He will do it.

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Note: See "Letter to a Friend Concerning the So-Called 'Lordship Salvation'" for a list of texts showing the necessity of holiness and the way this fits together with justification by faith and the freeness of grace and the reality of assurance.