Treasury of Scripture Knowledge
For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
So Sarai said to Abram, “Now behold, the Lord has prevented me from bearing children.
Please go in to my maid; perhaps I will obtain children through her.” And Abram listened to the voice of Sarai.
Then the Lord took note of Sarah as He had said, and the Lord did for Sarah as He had promised.