2Beloved, 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, because we shall see him as he is. 3And everyone who thus hopes in him purifies himself as he is pure. 4Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness. 5You know that he appeared in order to take away sins, and in him there is no sin. 6No one who abides in him keeps on sinning; no one who keeps on sinning has either seen him or known him. 7Little children, let no one deceive you. Whoever practices righteousness is righteous, as he is righteous. 8Whoever makes a practice of sinning is of the devil, for the devil has been sinning from the beginning. The reason the Son of God appeared was to destroy the works of the devil. 9No one born of God makes a practice of sinning, for God’s seed abides in him, and he cannot keep on sinning because he has been born of God. 10By this it is evident who are the children of God, and who are the children of the devil: whoever does not practice righteousness is not of God, nor is the one who does not love his brother. i Jn. 3:2–10, ESV.
As we consider the theological and practical implications of sanctification, bear in mind the state of your own heart and consider the scripture above. We must seriously reflect on our relationship with holiness if we are to claim a desire for an eternity of it with God. To understand holiness, we must understand sanctification. Although different theologians throughout history have taken disparate approaches to details of sanctification, it’s generally agreed that two kinds of sanctification exist in scripture: definitive (referring to our being made holy by the blood of Christ) and progressive (or the process by which our minds, hearts, and lives are brought into accord with the will of God).
Charles Spurgeon commented that the first step to understanding the two forms of sanctification is to grasp that one is finished and one is ongoing. The first is a synonym with “holy”: it means to be set apart. The “sanctified” are therefore those whom God, in His infinite wisdom, has called to be His children. This is perhaps the sense we see in Hebrews 10:14: “they [the children of God] that are sanctified,” are “by one offering [the King-Lamb Jesus Christ] … forever perfected.” The full Godhead works in the “already but not yet” of sanctification. By the decree of God our Father, we are already sanctified children of the King. This means that we are set apart for God’s purposes; we have been consecrated to his service. Moreover, because Christ’s blood has been sprinkled on us, we are able to approach God directly—to have intimacy with our father. As Paul said, “you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, ’Abba! Father!’”
The second sense of sanctification is the not yet. Progressive sanctification refers to God’s redemptive process, often seen in the Old Testament. There, we see the Hebrews engaging in rituals, like washing or sacrificing animals, to strip away the curses that came from Genesis 3 and kill the sin that results in wrong-hearted living because it causes separation from a perfect God. The Israelites had a set of obligatory rituals through which they sought cleanliness—this obedience was intended to counteract the rebellion of Adam that resonated throughout mankind. Because of Christ’s sacrifice, progressive sanctification now comes through Holy Spirit empowered, grace-driven effort to deny the sinful nature of our flesh and embrace the righteous lives owed to our Heavenly Creator. As Spurgeon said, “[God] subdues our corruptions, imparts to us graces, and leads us onward in the divine walk and life of faith.”
Progressive sanctification is made possible only because of the definitive sanctification imputed to us through the blood of Christ Jesus, enabled by the work of the Holy Spirit. Although we know that we are “new creations in Christ Jesus,” Paul makes clear in Romans 7 that a war still rages in our hearts. Although we still live in a fallen world, the Holy Spirit is progressively sanctifying us so our affections, thoughts, and actions are reordered in accordance with God’s will. In short, progressive sanctification is a weapon with which we can make war on the sin nature that once indwelled us.
This leads to an important question: What does understanding sanctification mean to us in our daily lives? Primarily, it means that we should be unafraid to run to our Father in Heaven when our hearts groan because He has chosen us to be his children. Furthermore, grasping the doctrine of sanctification exhorts us to rest in the blessed assurance that, by the blood of Christ, we can resist temptation and our flesh is enticing us into sin. Sprinkled with the blood of Christ, set apart for His service, sanctification is the process of God drawing us back to Eden. As the Holy Spirit works on us over time, we too can catch a glimpse of resplendent creation before the world was marred by Adam’s sin.
I hope it’s clear that this is not merely an intellectual exercise; it is a necessary part of our Christian lives. Remember the text we started with: “everyone who thus hopes in him purifies himself as he is pure. Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness.” Hope for purity so that you may be purified; put to death your practice of lawlessness so you may be found righteous; and put your trust in Jesus Christ, the master and perfecter of our faith.
 “For by one offering he hath perfected for ever them that are sanctified.” Hebrews 10:14, ESV.
 “So then, brothers, we are debtors, not to the flesh, to live according to the flesh. For if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body, you will live. For all who are led by the Spirit of God are sons of God. For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, ‘Abba! Father!’” Romans 8:12–15, ESV.
 “From now on, therefore, we regard no one according to the flesh. Even though we once regarded Christ according to the flesh, we regard him thus no longer. Therefore, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come. All this is from God, who through Christ reconciled us to himself and gave us the ministry of reconciliation; that is, in Christ God was reconciling[fn] the world to himself, not counting their trespasses against them, and entrusting to us the message of reconciliation.” ii Cor. 5:16–19, ESV.
To understand holiness, we must understand sanctification.