1 Samuel 16

1 Samuel 16:14-15

Therefore, when a person falls from the Spirit for any wickedness, if he repents after his fall, the grace remains irrevocably to the one who is willing; otherwise he who has fallen is no longer in God (because that Holy Spirit and Paraclete which is in God has deserted him), but this sinner shall be in him to whom he has subjected himself, as took place in Saul's instance; for the Spirit of God departed from him and an evil spirit was afflicting him. — Discourses Against the Arians 3.25.25