City of God

Now when a promise so great and clear was made to Abraham, in which it was so plainly said to him, “I have made you a father of many nations, and I will increase you exceedingly, and I will make nations of you, and kings shall go forth of you. And I will give you a son of Sarah; and I will bless him, and he shall become nations, and kings of nations shall be of him,” — a promise which we now see fulfilled in Christ—from that time forward this couple are not called in Scripture, as formerly, Abram and Sarai, but Abraham and Sarah, as we have called them from the first, for every one does so now.

The reason why the name of Abraham was changed is given: “For,” He says, “I have made you a father of many nations.” This, then, is to be understood to be the meaning of Abraham; but Abram, as he was formerly called, means “exalted father.” The reason of the change of Sarah's name is not given; but as those say who have written interpretations of the Hebrew names contained in these books, Sarah means “my princess,” and Sarai “strength.” Whence it is written in the Epistle to the Hebrews, “Through faith also Sarah herself received strength to conceive seed.” For both were old, as the Scripture testifies; but she was also barren, and had ceased to menstruate, so that she could no longer bear children even if she had not been barren.

Further, if a woman is advanced in years, yet still retains the custom of women, she can bear children to a young man, but not to an old man, although that same old man can beget, but only of a young woman; as after Sarah's death Abraham could of Keturah, because he met with her in her lively age. This, then, is what the apostle mentions as wonderful, saying, besides, that Abraham's body was now dead; because at that age he was no longer able to beget children of any woman who retained now only a small part of her natural vigor.

Of course we must understand that his body was dead only to some purposes, not to all; for if it was so to all, it would no longer be the aged body of a living man, but the corpse of a dead one. Although that question, how Abraham begot children of Keturah, is usually solved in this way, that the gift of begetting which he received from the Lord, remained even after the death of his wife, yet I think that solution of the question which I have followed is preferable, because, although in our days an old man of a hundred years can beget children of no woman, it was not so then, when men still lived so long that a hundred years did not yet bring on them the decrepitude of old age.