City of God

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 savor 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; 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.