The Westminster Confession of Faith in Plain Language1. God begins the process of sanctification by creating a new heart and spirit in those he has called and regenerated. He continues it by making them holier in the way they live out their lives day by day. This increase in holiness is guided and empowered by the Word of God and the Holy Spirit. It is made possible because Christ’s death and resurrection destroys the power of sin in their lives. Their sinful desires grow weaker and weaker and eventually die, and their ability to practice true holiness grows stronger and stronger. This process of sanctification is part and parcel of being a Christian—those who are not being sanctified in this way will never have the privilege of seeing the Lord face to face.
2. Sanctification makes the whole person holier—both the inner spiritual being and the outward way of life. Nevertheless, believers will never be completely perfect this side of eternity. There will always be some element of sinfulness that remains within. It causes a difficult and constant battle inside of them—their sinfulness wages war with the Holy Spirit, and the Holy Spirit wages war with their sinfulness.
3. In this war, remaining sinfulness can sometimes seem to get the upper hand for a while. But believers have a constant supply of strength from the Holy Spirit. This means that, ultimately, the believer’s new heart and spirit will win the battle. Those who believe in Christ will always grow in grace, becoming holier and holier, as they submit themselves to God.