Musnad Ahmad 907:33

Bahz narrated to us, Hammad ibn Salamah narrated to us, Simak narrated to us, he said: I heard Jabir ibn Samurah saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Islam will continue to be mighty until twelve caliphs." Then he said a hidden word that I did not understand. He said: I said to my father, "What did he say?" He said: "He said: 'All of them are from Quraysh.'"