Genesis 25:19-24

19These are the generations of Isaac, Abraham's son: Abraham fathered Isaac,

20and Isaac was forty years old when he took Rebekah, the daughter of Bethuel the Aramean of Paddan-aram, the sister of Laban the Aramean, to be his wife.

21And Isaac prayed to the Lord for his wife, because she was barren. And the Lord granted his prayer, and Rebekah his wife conceived.

22The children struggled together within her, and she said, "If it is thus, why is this happening to me?" So she went to inquire of the Lord.

23And the Lord said to her, "Two nations are in your womb, and two peoples from within you shall be divided; the one shall be stronger than the other, the older shall serve the younger."

24When her days to give birth were completed, behold, there were twins in her womb.