There is a start to sanctification (growth into Christlikeness), that is a moral change that starts at a specific point in life. Paul expresses this as a “washing of the Holy Spirit” (Titus 3:5, 1 Cor 6:11). This initial past category of sanctification involves the breaking off from the power of sin (Rom 6:11). Past sanctification is not progressive but is a one-time setting aside to holiness. In a sense this is a positional sanctification. Since we are justified in Christ and born again, we can no longer make a habit or pattern of sinning (1 John 3:9). This past sanctification is necessary because it is the power to break free and keep us from yielding to a life of sin and death. This is not to imply that we are completely free from sin, yet on the other side we cannot say that we are defeated by sin (Rom 6:14).
Sanctification that increases in the present can also be considered as progressive sanctification (1 Thess 4:3). This is a work that continues throughout our earthly lives. Wayne Grudem has a helpful definition; “Sanctification is a progressive work of God and man that makes us more and more free from sin and like Christ in our actual lives.”[1]This recognizes that sin remains in our lives and we are to not let sin reign in our mortal bodies ( Rom 6:12-13). Paul continues to articulate the concept of growing in sanctification, to more and more Christlikeness (Phil 3:9-14). The New Testament spends a significant amount of time exhorting believers to grow in the likeness of Christ. The moral commands can be considered part of the encouragement to sanctification as they are relying on the finished work of Christ. This need to strive for sanctification cannot be used as an excuse to continue in sin as it goes contrary to the teaching in Romans 6 about the resurrection power of Christ that enables us to overcome sin. The remaining sins in mature Christians should be less outwardly noticeable but the inward sins and attitudes of the heart and desires that are contrary to the will of God. Their zeal for in loving others and God should be matchless. Yet they are still sinners and sin showing how far we still fall short.
Our future sanctification is completed at death. Only when we arrive in the presence of God will we be made perfect (Heb 12:23). Sin remains after we become Christians (Rom 6:12-13; 1 John 1:8), our sanctification will never be completed in this life and so it follows that only in the future will our sanctification to be complete. Nothing unclean can enter the presence of God and the heavenly city (Rev 21:27). This sanctification involves the whole person as our bodies will also be included in the new heavens and new earth (2 Cor 7:1; 1 Thess 5:23; Phil 3:21).
[1] Grudem, Wayne A.. Systematic Theology: An Introduction to Biblical Doctrine (Cómo Entender) (p. 746). Zondervan. Kindle Edition.