Treasury of Scripture Knowledge
For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
Sarai said to Abram, "See now, Yahweh has restrained me from bearing. Please go in to my handmaid. It may be that I will obtain children by her." Abram listened to the voice of Sarai.
Yahweh visited Sarah as he had said, and Yahweh did to Sarah as he had spoken.