Genesis 25:19-24

19And these are the generations of Isaac, Abraham’s son: Abraham begat Isaac: 20And Isaac was forty years old when he took Rebekah to wife, the daughter of Bethuel the Syrian of Padan–aram, the sister to Laban the Syrian. 21And Isaac intreated Yhwh for his wife, because she was barren: And Yhwh was intreated of him, and Rebekah his wife conceived. 22And the children struggled together within her; and she said, If it be so, why am I thus? And she went to enquire of Yhwh. 23And Yhwh said unto her, Two nations are in thy womb, and two manner of people shall be separated from thy bowels; and the one people shall be stronger than the other people; and the elder shall serve the younger.

24And when her days to be delivered were fulfilled, behold, there were twins in her womb.