Genesis 25:4

And the sons of Midian: Ephah, and Epher, and Hanoch, and Abidah, and Eldaah. All these were the children of Keturah. The rich blessing of God shows that there was no stain attaching to this second marriage, but that it was entered into in sanctification and honor, for mutual care and assistance and for the procreation of children, the strength of Abraham having been retained in a remarkable manner, even to extreme old age. The children and grandchildren of Keturah, like those of Ishmael, became the forefathers of Arabian tribes, chiefly along the Ailanitic Gulf and northeast of it (Midianites), along the Red Sea, and along the Persian Gulf, most of them commercial nations.