It is narrated from Sayyiduna Sahar (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: The Hour will not be established until several tribes are swallowed up by the earth. (When a tribe is swallowed up,) it will be asked: Who among the such-and-such tribe has survived? Sayyiduna Sahar (may Allah be pleased with him) says: When the Prophet (peace and blessings be upon him) mentioned tribes, I understood that these would be Arab people, because non-Arabs are referred to by the names of their towns.