Moralia in Job
Oh, and while we're at it let's have a quick story:
"Another tells us how on retiring to his cell after matins to resume his studies, directly he fixed his eyes on the book he used to go to sleep. After rubbing his eyes to no purpose he thought within himself: 'Well, this is something strange, for I have had more sleep than usual, and yet I feel drowsy.' Straightway a voice resounded: 'It comes of not shutting the gates.' 'How then are they to be shut?' he enquired; and again the answer came, 'Shut them from the forehead to the breast, and from shoulder to shoulder.' Catching at the meaning he made the sign of the cross, saying, 'Depart from me, ye spirits of evil, and I will search into the word of my Lord.' "