Sanctification is one of those religious sounding words that people in the church use, but may not understand what it means. In its most basic sense, to sanctify something is to set it apart for God’s special use and purpose. Therefore, God’s people are sometimes said to be sanctified because they are set apart for God’s special purposes in the world: “Consecrate yourselves, therefore, and be holy; for I am the LORD your God. Keep my statutes, and do them; I am the LORD who sanctifies you” (Lev 20:7–8). As this verse helps us see, the word sanctification is closely related to holiness. The word sanctification can be used in a similar sense in the New Testament, and in one sense, believers are already sanctified because of what Jesus has done for them. Hebrews 10:10 tells us that as followers of Christ “we have been sanctified through the offering of the body of Jesus Christ once for all.”

Let’s define it

According to the Westminster Shorter Catechism (Q. 35), sanctification is “the work of God’s free grace, whereby we are renewed in the whole man after the image of God and are enabled more and more to die unto sin and live unto righteousness.” It is a continuing change worked by God in us, freeing us from sinful habits and forming in us Christlike affections, dispositions, and virtues. It does not mean that sin is instantly eradicated, but it is also more than a counteraction, in which sin is merely restrained or repressed without being progressively destroyed. Sanctification is a real transformation, not just the appearance of one

The basic meaning of “sanctify” is to set apart to God, for His use. But God works in those whom He claims as His own to conform them “to the image of his Son” (Rom. 8:29). This moral renovation, in which we are increasingly changed from what we once were, flows from the agency of the indwelling Holy Spirit (Rom. 8:13; 12:1, 2; 1 Cor. 6:11, 19, 20; 2 Cor. 3:18; Eph. 4:22–24; 1 Thess. 5:23; 2 Thess. 2:13; Heb. 13:20, 21). God calls His children to holiness, and graciously gives what He commands (1 Thess. 4:4; 5:23).

Regeneration is birth; sanctification is growth. In regeneration, God implants desires that were not there before: the desire for God, for holiness, and for glorifying God’s name in the world; the desire to pray and worship; the desire to love and bring benefit to others. In sanctification, the Holy Spirit “works in you, both to will and to work” according to God’s purpose, enabling His people to fulfil their new, godly desires (Phil. 2:12, 13). Christians become increasingly Christlike, as the moral profile of Jesus (the “fruit of the Spirit”) is progressively formed in them (2 Cor. 3:18; Gal. 4:19; 5:22–25).

Regeneration is a momentary act, bringing a person from spiritual death to life. It is exclusively God’s work. Sanctification is an ongoing process, dependent on God’s continuing action in the believer, and consisting of the believer’s continuous struggle against sin. God’s method of sanctification is neither activism (self-reliant activity) nor apathy (God-reliant passivity), but human effort dependent on God (2 Cor. 7:1; Phil. 3:10–14; Heb. 12:14). Knowing that without Christ’s enabling we cannot do good works, but also that He is ready to strengthen us for all we have to do (Phil. 4:13), we “abide” in Christ, asking for His help constantly— and we receive it (Col. 1:11; 1 Tim. 1:12; 2 Tim. 1:7; 2:1).

What do we mean when we say sanctification? 

Most of the time when Christians use the word sanctification, they are referring to the progressive work of God to make a believer more like Jesus Christ. As such Paul can write, “For this is the will of God, your sanctification: that you abstain from sexual immorality” (1 Thes 4:3). He commands Christians to “present your members as slaves to righteousness leading to sanctification” (Rom 6:19). Because believers have been set free from their slavery to sin, “the fruit you get leads to sanctification and its end, eternal life” (Rom 6:22).