Sanctification is the continuation of regeneration or the new birth. In the new birth it is not the soul but the spirit that is born again. The soul remains prone to evil until its dying day. The greatest enemy to holiness is man's own nature, his soul. In conversion the Holy Spirit enters our human spirit and sets up residency within the believer to rule the self or soul from man's spirit. As our spirit, empowered by the Holy Spirit, gains ascendency over our soul, we grow spiritually and become more like Christ. The Bible calls this sanctification, we call this spiritual growth. The key to spiritual growth is the ascending of the spirit over soul.