In a wide sense, sanctification includes all effects of God's Word in man. In a narrow sense, sanctification is the spiritual growth that follows justification a Christian cooperates in this work; through the Holy Spirit's work faith is increased daily, love strengthened, and the image of God renewed. A believer's good works are not perfect; but sins of weakness are forgiven. Sanctification differs in the same Christian at different times.
God works sanctification only through the means of grace. The most comforting part of the doctrine of sanctification is that which speaks of the completion of sanctification in heaven
Luther on Sanctification Edit
Martin Luther, taught in his Large Catechism that Sanctification is only caused by the Holy Spirit through the powerful Word of God. The Holy Spirit uses churches to gather Christians together for the teaching and preaching of the Word of God.
Sanctification is the Holy Spirit's work of making us holy. When the Holy Spirit creates faith in us, he renews in us the image of God so that through his power we produce good works. These good works are not meritorious but show the faith in our hearts (Ephesians 2:8-10, James 2:18). Sanctification flows from justification. It is an on-going process which will not be complete or reach perfection in this life.
Christian Perfection (Entire Sanctification) Edit
Lutheran rejection Edit
Lutherans reject the teaching of Christian Perfectionism,  the Augsburg Confession of 1530 condemns "those who contend that some may attain to such perfection in this life that they cannot sin."
Lutherans, quoting Romans 7:14-25 and Philippians 3:12, believe that "although we will strive for Christian perfection, we will not attain it in this life".  Modern apologists further note that:
Our salvation is complete and is simply received by faith. Good works are the fruit of that faith. Good works show that we are saved, but have no part in saving us. Becoming more and more God-like in this life is the result of being saved. If we are saved by becoming more and more God-like, our salvation is in doubt because our being God-like is never perfect in this life. The troubled conscience will find little comfort in an incomplete process of theosis, but will find much comfort in God's declaration of full and free forgiveness.