Musnad Abu Ya'la al-Mawsili 118:71

Muhammad ibn Abi Bakr narrated to us, 'Amr ibn 'Asim narrated to us, Abu al-'Awwam narrated to us, from Ma'mar, from al-Zuhri, from Anas, who said: When the day of Hunayn arrived, the people fled from the Messenger of Allah, may Allah bless him and grant him peace, except for al-'Abbas ibn 'Abd al-Muttalib and Abu Sufyan ibn al-Harith. The Messenger of Allah, may Allah bless him and grant him peace, ordered that it be called out: "O companions of Surah al-Baqarah! O company of the Ansar!" Then the call intensified among the Banu al-Harith ibn al-Khazraj. When they heard the call, they came forward. By Allah, I likened them to nothing but camels coming to their young. When they met, the fighting became intense. The Messenger of Allah, may Allah bless him and grant him peace, said: "Now the furnace has heated up." He took a handful of white pebbles and threw them, saying: "They are defeated, by the Lord of the Ka'bah." 'Ali ibn Abi Talib, may Allah be pleased with him, was on that day the most intense of the people in fighting before him.