What is Sanctification?
Those who are united to Christ, effectually called and regenerated, have a new heart and a new spirit created in them through the efficacy of Christ's death and resurrection. Furthermore, they are also really and personally sanctified through the same means, by His Word and Spirit dwelling in them. The power of every part of the body of sin is destroyed, and its various lusts are increasingly weakened and put to death, and saving graces are increasingly brought to life and strengthened in them so that they practice true holiness without which no one shall see the Lord.
This sanctification extends throughout the whole person, yet it remains incomplete in this life. Some remnants of corruption still remain in every part, from which arise a continual and irreconcilable war,the flesh desiring what is contrary to the Spirit, and the Spirit what is contrary to the flesh.
In this war, the remaining corruption may often predominate for a time, yet, through the continual supply of strength from the sanctifying Spirit of Christ, the regenerate part gains the victory. So believers grow in grace, moving towards mature holiness in the fear of God, pressing on towards the heavenly life in gospel obedience to all the commands which Christ as Head and King has prescribed for them in His Word.