Musnad Abu Ya'la al-Mawsili 110:88

'Abd al-A'la ibn Hammad al-Narsi narrated to us, Mu'tamir ibn Sulayman narrated to us, from Mundhir, from Wahb, from Ibn 'Abbas, who said: The Prophet of Allah (peace and blessings of Allah be upon him) said: "Twelve thousand will emerge from Aden, supporting Allah and His Messenger. They are the best of those between me and them." Mu'tamir said: I think he said, "in the depths (al-a'maq)."