Q. 39. What is sanctification?
A. Sanctification is a 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.
But we ought always to give thanks to God for you, brothers beloved by the Lord, because God chose you as the firstfruits to be saved, through sanctification by the Spirit and belief in the truth. 2 Thessalonians 2:13
And to be renewed in the spirit of your minds, and to put on the new self, created after the likeness of God in true righteousness and holiness. Ephesians 4:23-24
So you also must consider yourselves dead to sin and alive to God in Christ Jesus. Romans 6:11