When [Anthony] once had a discussion with certain men who had come to him concerning the state of the soul and of what nature its place will be after this life, the following night one from above called him, saying, "Anthony, rise, go out and look." Having gone out therefore (for he knew whom he ought to obey) looking up, he beheld one standing and reaching to the clouds, tall, hideous, and fearful, and others ascending as though they were winged. And the figure stretched forth his hands, and some of those who were ascending were stayed by him, while others flew above, and having escaped heaven-ward, were borne aloft free from care. At such, therefore, the giant gnashed his teeth, but rejoiced over those who fell back. And immediately a voice came to Anthony, "Do you understand what you see?" And his understanding was opened, and he understood that it was the passing of souls, and that the tall being who stood was the enemy who envies the faithful. And those whom he caught and stopped from passing through are accountable to him, while those whom he was unable to hold as they passed upwards had not been subservient to him. So having seen this, and as it were being reminded, he struggled the more daily to advance towards those things which were before.
From the Life of Anthony by St. Athanasius the Great, Ch. 66.