Musannaf Ibn Abi Shayba 36:456

Al-Fadl ibn Dukayn narrated to us, he said: Yusuf ibn Suhayb narrated to us, from Abdullah ibn Buraydah, that the Messenger of Allah (may Allah bless him and grant him peace) on the day of Hunayn, the people retreated from him, and there remained with him no one except a man called Zayd, holding the rein of his grey mule, which was the one the Negus had gifted him. The Messenger of Allah (may Allah bless him and grant him peace) said: "Woe to you, O Zayd, call the people." So he called out: "O people, this is the Messenger of Allah calling you." But no one answered. At that, he said: "Woe to you, urge the Aws and the Khazraj." So he said: "O company of the Aws and the Khazraj, this is the Messenger of Allah calling you." But no one answered him. At that, he said: "Woe to you, call the Muhajirun, for Allah has a pledge upon their necks." He said: So Buraydah narrated to me that a thousand of them came forward, having cast away their scabbards and broken them, then they came to the Messenger of Allah (may Allah bless him and grant him peace) until victory was granted to them.