Musnad Ahmad 764:3

'Abd al-Razzaq narrated to us, from Ma'mar, from al-Zuhri, who said: 'Abd al-Rahman ibn Azhar used to narrate from Khalid ibn al-Walid ibn al-Mughirah that he went out on that day, and he was in charge of the cavalry, the cavalry of the Messenger of Allah (peace and blessings of Allah be upon him). Ibn Azhar said: I saw the Messenger of Allah (peace and blessings of Allah be upon him), after Allah had defeated the disbelievers and the Muslims had returned to their camps, walking among the Muslims and saying: "Who will guide me to the camp of Khalid ibn al-Walid?" He said: So I walked—or I hurried—in front of him, and I had reached the age of puberty, saying: "Who will guide me to the camp of Khalid ibn al-Walid?" until we made our way to his camp. Khalid was leaning against the rear of his saddle. The Messenger of Allah (peace and blessings of Allah be upon him) came to him and looked at his wound. Al-Zuhri said: And I think he said: And the Messenger of Allah (peace and blessings of Allah be upon him) blew upon it.