Shorter Catechism Q. 35. What is sanctification? A. 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.
Commentary: Another benefit of our union and communion with Christ that we receive in this life is sanctification. Our sin creates a twofold problem that prevents us from fellowship with God, namely, our guilt and pollution (or sinfulness). We stand condemned and we are under the dominion of sin. Salvation in Christ, therefore, provides a “double cure” by cleansing us from sin’s “guilt and power.” The benefit of justification deals with our guilt and sanctification deals with our sinfulness.
Sanctification refers to God working in us so that we are transformed and conformed to the image of his Son. Sin has affected every aspect of our being (note: this is what we mean by total depravity. It doesn’t mean we are as bad as we could be but that our whole being has been tainted by sin.) Therefore, God renews us “in the whole man” so that we will be made perfectly and completely pure.
As God works salvation in us, so we work it out with fear and trembling. We can do all things through Christ who strengthens us, which means that we can increasingly live an obedient life. We can put sin to death, and we can pursue righteousness and holiness. After all, we are God’s workmanship, created in Christ Jesus for good works.