1 Timothy 4:12, “Let no one look down on your youthfulness, but rather in speech, conduct, love, faith and purity, show yourself an example of those who believe.”
The last characteristic Paul says to represent as a young Christian is purity. Prior to this, he wrote in 1 Timothy 1:5, “The aim of our charge is love that issues from a pure heart and a good conscience and a sincere faith.” But how do we become pure of heart? Fortunately, Scripture gives us the answer, and it’s not complex: “And everyone who thus hopes in Him purifies himself as He is pure” (1 John 3:3). Our hope in Jesus is that we are no longer enslaved to sin, and we have this hope by faith. When we have faith in Jesus, He purifies our hearts and begins to make us holy in our baptism, enabling us to seek holiness. Now that we’re children of God, we are able to serve our Saviour.
Yet as pure people, what are acts of purity? First Thessalonians 4:3-8:
For this is the will of God: your sanctification, that you abstain from sexual immorality; that each of you know how to control his own body in holiness and honour, not in the passion of lust like the Gentiles, who do not know God; that no one transgresses and wrong his brother in this matter, because the Lord is an avenger in all these things, as we told you beforehand and solemnly warned you. For God has not called us for impurity, but holiness. Therefore, whoever disregards this, disregards not man but God, who gives His Holy Spirit to you.
This might seem works based, but I assure you, it is not. Luther said, “For Christ has gained for us not only grace, but also the gift of the Holy Ghost so that we obtain from Him not only forgiveness of sin, but also the ceasing from sin.” The word for “sanctification” in Greek is ἁγιασμός (hagiasmos), which can also be translated as “holiness.” So sanctification and holiness are the same thing—they’re interchangeable terms. Sanctification is the ability to live a holy life, and it is the Holy Spirit who enables us to live holy lives—to cease from sin.
Paul preached as a minister of Christ to the Gentiles so that they “may be acceptable, sanctified by the Holy Spirit” (Romans 15:16). The Holy Spirit begins sanctification in our baptism. Before Christ, it is impossible to choose holiness over sin. When we have the Holy Spirit, He gives us the ability to be holy over sin. This is what it means to be simul iustus et peccator (simultaneously saint and sinner). We still sin, but by the power of the Holy Spirit we can choose not to sin. This sanctification, however, is not complete until Christ returns. This is one of those “now/not yet” realities of Scripture—we are currently holy ones (ἃγιος, saints), but we will not be fully made holy until Christ’s return.
God promised He would give us His Holy Spirit in baptism. “I will sprinkle clean water on you, and you shall be clean from all your uncleanness, and from all your idols I will cleanse you. And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put My Spirit within you, and cause you to walk in My statutes and be careful to obey My rules” (Ezekiel 36:25-27). So sanctification in His Holy Spirit doesn’t make us perfect in our ways, but as He says, “careful to obey” His rules—the ability by His Spirit within us to be more cognisant of His holiness and thereby walk in it. For example, His Spirit enables us to abstain from sexual immorality—that is, premarital sex, adultery, pornography, homosexuality, etc. Yet remember as we are saints and sinners, our flesh and the Spirit God has given us are constantly in opposition to each other (Galatians 5:17). As sinners, sometimes our flesh will prevail. As saints, we will prevail over sin when we exercise the Spirit God has given us. Prevailing over sin is not possible without God’s Spirit, whom we receive in baptism.
By faith, Jesus purifies our hearts. Since antiquity, God promised us His Spirit so that we may be purified and able to live holy and pure lives as best as we are able, and He accomplished His will of sanctification through Jesus Christ who baptises us in God’s Holy Spirit as He continues to do His will in us through the continual sanctification of our baptism.