Sayyiduna Jabir bin Samurah (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) delivering a sermon, and he (peace and blessings be upon him) was saying: "Islam will remain mighty until twelve caliphs." Then he (peace and blessings be upon him) said something that I could not understand, so I asked: What did the Messenger of Allah (peace and blessings be upon him) say? He told me: He (peace and blessings be upon him) said: "All of them will be from Quraysh."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1951