1. The first part of the answer is found in our text of this chapter, I Thess. 5:23, "And the God of Peace himself sanctify you wholly and may your Spirit and soul and body be preserved entire, without blame at the coming of our Lord Jesus Christ."
It appears from this verse that God sanctifies men, and Sanctification is God's work. Both the separation of men from sin and their separation unto God, is God's work. As it was God who in the old dispensation set apart the first-born of Israel unto Himself, so it is God who in the new dispensation sets apart the believer unto Himself and separates him from sin. Sanctification is primarily not our work but God's.
2. The second part of the answer is found in Eph. 5:25, 26, "Husbands love your wives, even as Christ also loved the church, and gave himself up for it; that he might sanctify it, having cleansed it by the washing of water by the word." Here we are taught that Christ sanctifies the church and that Sanctification is Christ's work. The question, of course, arises, in what sense does Christ sanctify the church. The answer is found in Heb. 10:10, "By which will we have been sanctified through the offering of the body of Jesus Christ once for all." Here it appears that Jesus Christ sanctifies the church by giving Himself up a sacrifice for it. By thus giving Himself up for it as a sacrifice Christ sets the Church apart for God. Just as the blood of the Passover Lamb in the 11th and 12th chapters of Exodus set a difference between Israel and the Egyptians, so our Lord Jesus by the offering of His own body has forever put a difference between the believer in Himself and the world, and has forever set every believer apart for God. The Cross of Christ stands between the
believer and the world. The shed blood of Christ separates the believer from the world, purchases him to God and thus makes him to belong to God.
3. The third part of the answer to the question, how men are sanctified, is found in 2 Thess. 2:13 and in other passages, "But we are bound to give thanks always to God for you, brethren beloved of the Lord, for that God chose you from the beginning unto salvation through sanctification of the Spirit and belief of the truth." It appears from this passage, as from other passages in the Bible, that it is the Holy Spirit who sanctifies the believer, and that Sanctification is the Holy Spirit's work. Here the question arises, In what sense does the Holy Spirit sanctify the believer? In this sense, just as in the Old Testament type, tabernacle, altar and priest were set apart for God by the anointing oil (Lev. 8:10-12), so in the New Testament anti-type, the believer, who is both tabernacle and priest, is set apart for God by the anointing of the Holy Spirit. Further than that, it is the Holy Spirit's work in the heart that overcomes the flesh and its defilements, and thus separates the believer from sin and clothes him with divine graces of character, and makes him fit to be God's own. As Paul puts it in Gal. 5:22, 23, "But the fruit of the Spirit is love, joy, peace, longsuffering, kindness, goodness, faith, meekness, self-control." In opposition to this work of the Holy Spirit, we read in the immediately preceding verses what "the works of the flesh" are, an awful
catalogue of vileness and sin, and we are told in the 16th verse, "Walk in the Spirit and ye shall not fulfil the lust of the flesh."
4. The fourth part of the answer to the question how we are sanctified is found in Heb. 13:12, "Wherefore, Jesus also, that he might sanctify the people through his own blood suffered without the gate." It is plain from this passage that believers are sanctified through the blood of Jesus Christ. Here the question arises, In what sense does the blood of Jesus sanctify? The answer is plain: The blood of Jesus Christ cleanses us from all the guilt of sin, and thus separates us from the mass of men under the curse of the broken law, and sets us apart for God (cf. 1 John 1:7, 9). In the Old Testament dispensation the blood of the sacrifice cleansed the Israelites from the guilt of ceremonial offenses and set them apart for God; in the New Testament anti-type the blood of Christ cleanseth the believer from the guilt of moral offenses and sets him apart for God.
5. The fifth part of the answer to the question, how men are sanctified, is found in John 17:17, "Sanctify them in the truth: thy word is truth." Here our Lord Jesus in His prayer indicates that we are sanctified in the truth, and that the truth is the Word of God. In what sense does the Word of God sanctify? This question is plainly answered in different parts of the Word of God, where we are taught that the Word of God cleanses from the presence of sin, and thus
separates us from it and sets us apart to God. (Ps. 119:9, 11; John 15:3.) As we bring our lives into daily contact with the Word, the sins and imperfections of our lives and hearts are disclosed and put away, and thus we are more and more separated from sin unto God. (cf. John 13:10.)
6. The sixth part of the answer to the question, how men are sanctified, is found in 1 Cor. 1:30, "But of Him are ye in Christ Jesus, who was made unto us wisdom from God, and righteousness, and sanctification, and redemption." In this passage we are taught that Jesus Christ was made unto us from God sanctification. Just what does that mean? Simply this: that separation from sin and separation to God are provided for us in Christ Jesus and by the appropriation of Jesus Christ we obtain this sanctification thus provided. The more completely we appropriate Christ the more completely are we sanctified. But perfect sanctification is provided for us in Him, just as perfect wisdom is provided in Him (Col. 2:3). We appropriate either wisdom or sanctification or anything else that is provided for us in Christ in ever-increasing measure. Through the indwelling Christ presented to us by the Spirit in the Word, we are made Christlike and bear fruit.