Musnad Ahmad 26:786

'Affan narrated to us, 'Abd al-Wahid ibn Ziyad narrated to us, al-Harith ibn Hasirah narrated to us, al-Qasim ibn 'Abd al-Rahman narrated to us, from his father, who said: 'Abdullah ibn Mas'ud said: I was with the Messenger of Allah, peace and blessings of Allah be upon him, on the day of Hunayn. He said: The people turned away from him, and eighty men from the Emigrants (Muhajirun) and the Helpers (Ansar) remained firm with him. We retreated on our feet about eighty paces, and we did not turn our backs to them. They are the ones upon whom Allah, the Mighty and Majestic, sent down tranquility. He said: The Messenger of Allah, peace and blessings of Allah be upon him, was on his mule, moving forward, when his mule swerved, and he leaned from the saddle. I said to him, "Rise, may Allah raise you." He said, "Hand me a handful of dust." So he struck their faces with it, and their eyes were filled with dust. Then he said, "Where are the Emigrants and the Helpers?" I said, "They are here." He said, "Call out to them." So I called out to them, and they came with their swords in their right hands, as if they were shooting stars, and the polytheists turned their backs.