Abu Dawud
The Promised Deliverer
Book Number: 031 / Hadith Number: 4277
Narated By Ali ibn Abu Talib : The Prophet (pbuh) said: A man called al-Harith ibn Harrath will come forth from Ma Wara an-Nahr. His army will be led by a man called Mansur who will establish or consolidate things for Muhammad's family as Quraysh consolidated them for the Apostle of Allah (pbuh). Every believer must help him, or he said: respond to his sermons.