Al-'Abbas bin 'Abdul-Muttalib (May Allah be pleased with him) said

I was in the company of the Messenger of Allah (ﷺ) on the day of (the battle of) Hunain. Abu Sufyan bin Al-Harith and I did not leave the Messenger of Allah (ﷺ) throughout the battle. The Messenger of Allah (ﷺ) was riding on his white mule. When the Muslims had an encounter with the pagans, Muslims took to their heels. The Messenger of Allah (ﷺ) began to urge his mule towards the disbelievers, holding the bridle of his mule. I was trying to restrain it from going very fast, and Abu Sufyan was holding the stirrup of the mule of the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) said, "O Abbas! Call out the People of As-Samurah [i.e., those people who had made the covenant under the tree (i.e., Bai'ah Ridwan)]." 'Abbas called out at the top of his voice: "Where are the People of As-Samurah." 'Abbas said: As soon as they heard my voice, they rushed towards the Prophet (ﷺ) like a cow turning towards her calf. They were shouting: "Here we are." Soon they began to fight the infidels. Then there was a call for Ansar. Those who called out to them shouted: "O you the people of Ansar! O you the people of Ansar!" They ended their call at Banu Al-Harith bin Al-Khazraj. The Messenger of Allah (ﷺ) who was riding on his mule looked at their fight with his neck stretched forward and he said, "This is the time when the fight is raging hot." Then the Messenger of Allah (ﷺ) took pebbles and threw them in the face of the disbelievers. He said, "By the Rubb of Muhammad, the disbelievers will be defeated." I continued to watch until I found that their force was subdued and they began to retreat.

[Muslim].