https://sunnah.com/abudawud/38/13
Narrated Ali ibn AbuTalib:
The Prophet (ﷺ) 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 Messenger of Allah (ﷺ). Every believer must help him, or he said: respond to his sermons.
Grade: Da'if (Al-Albani)