Musnad Ahmad 658:73

Yahya ibn Sa'id narrated to us, Sufyan narrated to us, Abu Ishaq narrated to me, he said: A man said to al-Bara': "O Abu 'Umarah, did you flee on the day of Hunayn?" He said: "No, by Allah, the Prophet, may Allah bless him and grant him peace, did not flee. But the hasty ones among the people fled, and Hawazin met them with arrows." He said: "I saw the Prophet, may Allah bless him and grant him peace, on his white mule, and Abu Sufyan ibn al-Harith was holding its bridle, and he was saying: 'I am the Prophet, there is no lie; I am the son of 'Abd al-Muttalib.'"