1 John 4:4-6

Ye are of God, my little children, and have overcome them: because greater is he that is in you than he that is in the world. They are of the world: therefore speak they as of the world, and the world heareth them. We are of God: he that knoweth God heareth us; he who is not of God heareth us not. By this we know the spirit of truth, and the spirit of error.