Genesis 25:19 (KJV)

And Mishma, and Dumah, and Massa,

Hadar, and Tema, Jetur, Naphish, and Kedemah:

These are the sons of Ishmael, and these are their names, by their towns, and by their castles; twelve princes according to their nations.

And these are the years of the life of Ishmael, an hundred and thirty and seven years: and he gave up the ghost and died; and was gathered unto his people.

And they dwelt from Havilah unto Shur, that is before Egypt, as thou goest toward Assyria: and he died in the presence of all his brethren.

And Isaac was forty years old when he took Rebekah to wife, the daughter of Bethuel the Syrian of Padanaram, the sister to Laban the Syrian.

And Isaac intreated the LORD for his wife, because she was barren: and the LORD was intreated of him, and Rebekah his wife conceived.

And the children struggled together within her; and she said, If it be so, why am I thus? And she went to enquire of the LORD.

And the LORD 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.

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