Genesis 25:16

These are the sons of Ishmael, and these are their names by their towns and by their castles; twelve princes according to their nations. As the Lord had promised Hagar, so it came to pass: twelve princes were begotten of her son Ishmael, twelve mighty sheiks of powerful tribes, the names of some of which were preserved for many centuries. Thus the descendants of Nebajoth and Kedar lived in Arabia Petraea, on the Peninsula of Sinai, and beyond, Isaiah 60:7, the Kadarenes afterward extending toward the east in the direction of Babylonia, Isaiah 42:11; Psalms 120:5. The other Iahmaelitic tribes do not seem to have been so large and mighty, still there are references, also in Scripture, which place them into the great country on the east side of Jordan. Twelve princes they were in their tribes, governing and representing twelve tribes, with their permanent, walled camps, or cities, and their temporary encampments, with their fixed and movable habitations.