The Ladder of Divine Ascent – Step 3, Last Paragraph

29. Devils often transform themselves into angels of light and take the form of martyrs, and make it appear to us during sleep that we are in communication with them. Then, when we wake up, they plunge us into unholy joy and conceit. But you can detect their deceit by this very fact. For angels reveal torments, judgments and separations; and when we wake up we find that we are trembling and sad. As soon as we begin to believe the devils in dreams, then they make sport of us when we are awake, too. He who believes in dreams is completely inexperienced. But he who distrusts all dreams is a wise man. Only believe dreams that foretell torments and judgment for you. But if despair afflicts you, then such dreams are also from devils.
This is the third step, which is equal in number to the Trinity. He who has reached it, let him not look to the right hand nor to the left.