Spiritual Theology (Ascetical Theology): Sanctification
Sanctification is central to spiritual theology and to the Christian life as a whole. It is the ongoing process by which God separates His people from sin, setting them apart for holiness and conformity to Christ. In ascetical theology, which studies the pursuit of holiness through discipline and devotion, sanctification occupies a prominent place. Unlike justification, which addresses the guilt of sin, sanctification addresses its power and pollution, gradually transforming believers into the likeness of Christ.
This doctrine emphasizes both God’s initiative and the believer’s cooperation. The Spirit is the primary agent of sanctification, but Christians are called to walk in obedience, prayer, and discipline as they are conformed to the image of Christ. Sanctification is never a static condition but a lifelong journey that finds its completion only in glorification.
1. The Biblical Foundation of Sanctification
The concept of sanctification is deeply embedded in both the Old and New Testaments. In the Old Testament, God set apart Israel to be His holy people (Leviticus 20:26). Holiness was not merely moral purity but being consecrated to God’s service.
In the New Testament, sanctification takes on a Christ-centered dimension. Paul declares that Christ Himself has been made our sanctification (1 Corinthians 1:30). Believers are described as “saints,” those who are holy by virtue of their union with Christ (Romans 1:7). This shows that sanctification is both a status—being set apart in Christ—and a process of growth in holiness.
Jesus prayed for His disciples: “Sanctify them in the truth; your word is truth” (John 17:17). This prayer reflects both the divine initiative and the human response: God sanctifies through His Word, and believers grow in holiness by receiving and living out that Word.
2. The Distinction Between Justification and Sanctification
Sanctification is closely linked to justification, but the two must be distinguished. Justification is a legal declaration in which God pronounces sinners righteous on the basis of Christ’s work. It deals with guilt. Sanctification, however, deals with the ongoing corruption of sin and the believer’s transformation into Christlikeness.
While justification is an instantaneous act, sanctification is progressive. Justification changes a believer’s standing before God, whereas sanctification changes the believer’s life over time. Together, they reveal the comprehensive scope of salvation: God not only forgives sin but also delivers His people from its power.
3. The Role of the Holy Spirit in Sanctification
The Holy Spirit is the primary agent of sanctification. Paul writes, “God chose you as the firstfruits to be saved, through sanctification by the Spirit and belief in the truth” (2 Thessalonians 2:13). The Spirit indwells believers, convicting them of sin, empowering obedience, and producing the fruit of holiness.
The Spirit’s role is not merely external guidance but internal transformation. Believers are born from above (John 3:5–8), and this new birth inaugurates the process of sanctification. From there, the Spirit continues to shape their desires, renew their minds, and strengthen their wills for obedience.
4. Human Cooperation in Sanctification
Although sanctification is primarily God’s work, it requires human response. Paul exhorts believers: “Work out your own salvation with fear and trembling, for it is God who works in you” (Philippians 2:12–13). The paradox is that while God works, believers are not passive. They must pursue holiness intentionally.
Spiritual disciplines—such as prayer, fasting, worship, Scripture reading, and service—function as means of grace. These practices do not sanctify in themselves but place believers in the path of God’s transforming work. Ascetical theology emphasizes these disciplines as ways of aligning human effort with divine initiative.
5. The Objective and Subjective Dimensions of Sanctification
Sanctification is both an objective reality and a subjective experience. Objectively, believers are sanctified in Christ. Hebrews 10:10 declares, “We have been sanctified through the offering of the body of Jesus Christ once for all.” In this sense, sanctification is complete because it is grounded in Christ’s finished work.
Subjectively, sanctification is an ongoing process. Believers grow in grace, putting off the old self and putting on the new (Ephesians 4:22–24). This progressive dimension highlights the daily struggle against sin and the pursuit of holiness. The tension between the already and not-yet characterizes the Christian journey.
6. The Imperfection of Sanctification in This Life
A critical truth of sanctification is that perfection is not attainable in this life. While believers are called to holiness, they remain in constant battle with sin. John reminds the church: “If we say we have no sin, we deceive ourselves, and the truth is not in us” (1 John 1:8).
This imperfection should not lead to despair but to hope. The incomplete sanctification of believers points forward to glorification, when Christ will present His church “without spot or wrinkle…holy and without blemish” (Ephesians 5:27). The struggle itself is evidence of the Spirit’s presence, as believers groan for full redemption (Romans 8:23).
7. Sanctification and the Gospel
Sanctification cannot be separated from the gospel. The good news is not only that Christ forgives sins but also that He transforms sinners into saints. The gospel frees believers from the dominion of sin, enabling them to live in righteousness.
Anthony Delgado’s perspective on the gospel as the kingdom’s expansion highlights sanctification as participation in God’s reign. As believers are sanctified, they embody the reality of God’s kingdom on earth. This transformative aspect of the gospel is vital for Christian witness, for a sanctified life demonstrates the power of Christ’s rule.
8. The Eschatological Fulfillment of Sanctification
Sanctification points forward to its completion in the last days. When Christ returns, believers will be glorified—perfected in holiness and freed entirely from sin. Paul writes, “He who began a good work in you will bring it to completion at the day of Jesus Christ” (Philippians 1:6).
In this way, sanctification is both present and future. Believers are sanctified now, growing in holiness, while awaiting the final transformation. This eschatological hope sustains Christians as they persevere in faith and holiness amid trials and temptations.
Conclusion
Sanctification is a central theme in spiritual theology, encompassing God’s work in setting apart His people and their cooperation in living holy lives. It is grounded in the work of Christ, empowered by the Spirit, and expressed in the daily pursuit of holiness. While perfection will only come at glorification, the process of sanctification is evidence of God’s ongoing work in His people.
This doctrine reminds believers that salvation is more than a legal declaration. It is a transformative journey into holiness, shaping every aspect of life and pointing toward the eternal hope of glory.
Bible Verses about Sanctification
“Sanctify them in the truth; your word is truth.” (John 17:17)
“For this is the will of God, your sanctification: that you abstain from sexual immorality.” (1 Thessalonians 4:3)
“But now that you have been set free from sin and have become slaves of God, the fruit you get leads to sanctification and its end, eternal life.” (Romans 6:22)
“And by that will we have been sanctified through the offering of the body of Jesus Christ once for all.” (Hebrews 10:10)
“Since we have these promises, beloved, let us cleanse ourselves from every defilement of body and spirit, bringing holiness to completion in the fear of God.” (2 Corinthians 7:1)
“And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.” (1 Corinthians 6:11)
“For God has not called us for impurity, but in holiness.” (1 Thessalonians 4:7)
“He who calls you is faithful; he will surely do it.” (1 Thessalonians 5:24)
“Beloved, we are God’s children now, and what we will be has not yet appeared; but we know that when he appears we shall be like him.” (1 John 3:2)
“But grow in the grace and knowledge of our Lord and Savior Jesus Christ.” (2 Peter 3:18)
