Abu Qabus narrates from his father, and he from his grandfather, who narrates from Sayyiduna Ali (may Allah be pleased with him) that he said: I came to the Prophet (peace and blessings be upon him) with the head of Marhab. Imam al-Shafi'i (may Allah have mercy on him) said: On the day of the Trench (Khandaq), Sayyiduna Ali (may Allah be pleased with him) fought Amr bin Abd Wudd in single combat.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18349