Herman Bavinck provides very thoughtful and clear teaching on the doctrine of sanctification. Sanctification presupposes effectual calling, regeneration, justification, and adoption. It is a work of God in us which manifests itself in faith and repentance, love, and obedience. Thus, it is primarily the work of the Holy Spirit.
To understand the benefit of sanctification correctly, we must proceed from the idea that Christ is our holiness in the same sense in which he is our righteousness. He is a complete and all-sufficient Savior. He does not accomplish his work halfway but saves us really and completely. He does not rest until, after pronouncing his acquittal in our conscience, he has also imparted full holiness and glory to us. By his righteousness, accordingly, he does not just restore us to the state of the just who will go scot-free in the judgment of God, in order then to leave us to ourselves to reform ourselves after God’s image and to merit eternal life. But Christ has accomplished everything. He bore for us the guilt and punishment of sin, placed himself under the law to secure eternal life for us, and then arose from the grave to communicate himself to us in all his fullness for both our righteousness and sanctification. (Reformed Dogmatics, 4.248)
Bavinck draws a helpful distinction between our holiness and our righteousness. Both are entirely a work of Christ and bestowed by grace. Christ secures our righteousness so that we are free from guilt and punishment, and he secures our holiness so we are free from the stain and pollution of sin.
Some caution must be offered. The security of our holiness by Christ does not imply that we no longer sin in this life. Instead, the intention is that though indwelling sin remains it does not reign or have mastery (to borrow a phrase from John Murray, Redemption Accomplished and Applied, 145). Sin is sin regardless of whether or not the person is redeemed. Sin’s character does not change. Sin does not become more palatable to God just because it flows from a believer. Likewise, this sets up a tension that the apostle Paul references in Romans 7:14ff,
14 For we know that the law is spiritual, but I am of the flesh, sold under sin. 15 For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. 16 Now if I do what I do not want, I agree with the law, that it is good. 17 So now it is no longer I who do it, but sin that dwells within me. 18 For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. 19 For I do not do the good I want, but the evil I do not want is what I keep on doing. 20 Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me.
The Holy Spirit’s presence serves to convict in the face of sin. This conviction grows as one fathoms God’s glory and grace. In this manner it can be said that such conviction in the face of sin is an affirmation to the ongoing work of the Holy Spirit.
Justification and sanctification, accordingly, while distinct from each other, are not for a moment separated. The distinction between the two consists in the fact that in justification the religious relationship of human beings with God is restored, and in sanctification their nature is renewed and cleansed of the impurity of sin. At bottom the distinction rests on the fact that God is both righteous and holy. As the Righteous One, he wants all his creatures to stand in relation to him in which he put them originally – free from guilt and punishment. As the Holy One, he demands that they will all appear before him pure and unpolluted by sin. (Reformed Dogmatics, 4.249)
In Christ our restoration is full and complete. Our relationship with God is restored, our guilt and punishment is satisfied by Christ, and we are now seen as holy for we bear Christ’s imputed righteousness.