Musnad Ahmad 907:31

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Simak ibn Harb, he said: I heard Jabir ibn Samurah, he said: I heard the Prophet of Allah, peace and blessings of Allah be upon him, saying: "There will be twelve commanders." Then he said a word I did not hear, so the people said: "All of them are from Quraysh."