On the Life of the Wise Man made perfect by Instruction or, on the Unwritten Law, that is to say, on Abraham (111-115)

Nevertheless he did not completely believe them even when they made him this promise, by reason of the incredible nature of the thing promised; for both he and his wife, through extreme old age, were so old as utterly to have abandoned all hope of offspring;

therefore the scriptures record that Abraham’s wife, when she first heard what they were saying, laughed; and when they said afterwards, "Is anything impossible to God?" they were so ashamed that they denied that they had laughed; for Abraham knew that everything was possible to God, having almost learnt this doctrine as one may say from his cradle;

then for the first time he appears to me to have begun to entertain a different opinion of his guests from that which he conceived at first, and to have imagined that they were either some of the prophets or of the angels who had changed their spiritual and soul-like essence, and assumed the appearance of men.

We have now then described the hospitable temper of the man, which was as it were a sort of addition to set off his greater virtue; but his virtue was piety towards God, concerning which we have spoken before, the most evident instance of which is to be found in his conduct now recorded towards the strangers;

but if any persons have fancied that house happy and blessed in which it has happened that wise men have stopped and abode, they should consider that they would not have done so, and would not even have looked into it at all, if they had seen any incurable disease in the souls of those who were therein, but I know not what excess of happiness and blessedness, I should say, existed in that house in which angels condescended to tarry and to receive the rites of hospitality from men, angels, those sacred and divine natures, the ministers and lieutenants of the mighty God, by means of whom, as of ambassadors, he announces whatever predictions he condescends to intimate to our race.