Sayyiduna Ali (may Allah be pleased with him) narrates: We came to Khaybar. When the Prophet (peace and blessings be upon him) arrived there, he sent Sayyiduna Umar (may Allah be pleased with him) and sent some people with him, but after a short while Sayyiduna Umar (may Allah be pleased with him) and his companions had to fall back. Then the Prophet (peace and blessings be upon him) said: "I will send to these people a man who loves Allah and His Messenger, and Allah and His Messenger love him. He will fight them until Allah Almighty grants that man victory." The narrator says: The people kept longing for this and kept raising their necks to look. After some time had passed, the Prophet (peace and blessings be upon him) asked: "Where is Ali?" The people said: "He is suffering from an eye inflammation." The Prophet (peace and blessings be upon him) said: "Call him and bring him to me." When I presented myself before the Prophet (peace and blessings be upon him), he opened my eyes and applied his saliva to them, then he gave me the banner. I set off and came to those people. Marhab came there reciting war poetry (rajaz), until, when the two of us met in combat, Allah Almighty routed him, and his companions were routed too. They shut themselves up in the fortress and closed the gate. We came to the gate and kept trying to get it opened, until Allah Almighty granted the conquest of it (the town or the fortress).
Al-Bazzar recorded it. Its chain contains a narrator, Nu'aym bin Hakim, whom Ibn Hibban and others declared thiqah (trustworthy), and there is some weakness in him.