Saint John Cassian. "Conferences".
The Second Conference of Abbot Moses. On Discretion.
Chapter VII. Of an illusion into which another fell for lack of discretion.
Why also should I speak of one (whose name we had rather not mention as he is still alive), who for a long while received a devil in the brightness of an angelic form, and was often deceived by countless revelations from him and believed that he was a messenger of righteousness: for when these were granted, every night he provided a light in his cell without the need of any lamp. At last he was ordered by the devil to offer up to God his own son who was living with him in the monastery, in order that his merits might by this sacrifice be made equal to those of the patriarch Abraham. And he was so far seduced by his persuasion that he would really have committed the murder unless his son had seen him getting ready the knife and sharpening it with unusual care, and looking for the chains with which he meant to tie him up for the sacrifice when he was going to offer him up; and had fled away in terror with a presentiment of the coming crime.