30. _Of Lot's deliverance from Sodom, and its consumption by fire from heaven; and of Abimelech, whose lust could not harm Sarah's chastity._
After this promise Lot was delivered out of Sodom, and a fiery rain from heaven turned into ashes that whole region of the impious city, where custom had made sodomy as prevalent as laws have elsewhere made other kinds of wickedness. But this punishment of theirs was a specimen of the divine judgment to come. For what is meant by the angels forbidding those who were delivered to look back, but that we are not to look back in heart to the old life which, being regenerated through grace, we have put off, if we think to escape the last judgment? Lot's wife, indeed, when she looked back, remained, and, being turned into salt, furnished to believing men a condiment by which to savour somewhat the warning to be drawn from that example. Then Abraham did again at Gerar, with Abimelech the king of that city, what he had done in Egypt about his wife, and received her back untouched in the same way. On this occasion, when the king rebuked Abraham for not saying she was his wife, and calling her his sister, he explained what he had been afraid of, and added this further, "And yet indeed she is my sister by the father's side, but not by the mother's;"[300] for she was Abraham's sister by his own father, and so near of kin. But her beauty was so great, that even at that advanced age she could be fallen in love with.
31. _Of Isaac, who was born according to the promise, whose name was given on account of the laughter of both parents._
After these things a son was born to Abraham, according to God's promise, of Sarah, and was called Isaac, which means _laughter_. For his father had laughed when he was promised to him, in wondering delight, and his mother, when he was again promised by those three men, had laughed, doubting for joy; yet she was blamed by the angel because that laughter, although it was for joy, yet was not full of faith. Afterwards she was confirmed in faith by the same angel. From this, then, the boy got his name. For when Isaac was born and called by that name, Sarah showed that her laughter was not that of scornful reproach, but that of joyful praise; for she said, "God hath made me to laugh, so that every one who hears will laugh with me."[301] Then in a little while the bond maid was cast out of the house with her son; and, according to the apostle, these two women signify the old and new covenants,--Sarah representing that of the Jerusalem which is above, that is, the city of God.[302]
