Musnad Ahmad 658:234

Yahya narrated to us, from Sufyan, Abu Ishaq narrated to me, from Al-Bara’ ibn ‘Azib, who said: A man said to him: "O Abu ‘Amarah, did you flee on the day of Hunayn?" He said: "No, by Allah, the Prophet, peace and blessings of Allah be upon him, did not flee. But the hasty ones among the people fled. Hawazin met them with arrows, while the Messenger of Allah, peace and blessings of Allah be upon him, was on a white mule, and Abu Sufyan ibn al-Harith was holding its bridle. The Messenger of Allah, peace and blessings of Allah be upon him, was saying: 'I am the Prophet, there is no lie; I am the son of ‘Abd al-Muttalib.'"