سمعتُ النبي يقول: يكون إثنا عشر أميراً. فقال كلمة لم أسمعها. فقال أبي كلُّهم من قريش.
In Musnad Ahmad, the tradition is as follows:
The Prophet (S) said: "There shall be twelve Caliphs
for this community, all of them from Quraish."
_________________
the Messenger of Allah (S) said:
He who dies while he does not know the Imam of his age, is like the one who died during days of Jahiliyya (the era before Islam).
من ماتً و لم يعرف إمام زمانهِ مات ميتة جاهلية.
______________