Unforgiveness is one of the biggest tools the devil uses against God’s people. It not only cuts us off from God’s forgiveness (Mark 6:15), but it also turns you over to the tormenters (Matthew 18:23-35), which are demons. You give demons legal grounds in your life when you are bitter and unforgiving against others. Unforgiveness is a sin which can defile a person (Hebrews 12:15). Unforgiveness in itself is a sin which should be repented of.