Musnad Ahmad 5:104

Muhammad ibn al-Sabah narrated to us, he said: Abdullah said: And I heard it myself from Muhammad ibn al-Sabah, Ismail ibn Zakariya narrated to us, from Kathir al-Nawa, from Abdullah ibn Mulayl, he said: I heard Ali saying: I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: "There was no prophet before me except that he was given seven chiefs (nuqaba'), ministers, and nobles. And I have been given fourteen ministers, chiefs, and nobles: seven from Quraysh and seven from the Emigrants (Muhajirun)."