Philoxenus of Mabbug

That is to say, do not grieve him by sin, otherwise his light will be quenched from your soul—a light which, when kindled within you, gives you the possession of a power that is beyond expression; and you will be able to contend "with principalities and powers," and fight against the evil spirits under heaven, and reject all the world with its pleasures and pains. All are effected by the fervor of the Spirit within us.