It is narrated from Sayyiduna Suhar (may Allah be pleased with him), who said: I heard the Messenger of Allah (peace and blessings be upon him) say: "The Hour will not be established until several tribes are swallowed up by the earth, until it is said: Who remains of such-and-such a tribe?" I understood that he (peace and blessings be upon him) meant the Arabs, because the non-Arabs ('Ajam) do not have tribes.
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7373