He was asked about the wounds the Messenger of Allah ﷺ sustained at the Battle of Uhud, and he replied, "The face of the Messenger of Allah ﷺ was wounded, his lower right tooth was broken, and his helmet was shattered upon his head. Fatimah, daughter of the Messenger of Allah ﷺ, was washing away the blood while Ali bin Abu Talib poured water for her with a shield. When Fatimah saw that the water was only making the bleeding worse, she took a piece of a straw mat and burned it until it turned to ash, then pressed it against the wound, and the bleeding stopped."
يسأل عن جرح رسول الله ﷺ يوم أحد فقال: جرح وجه رسول الله ﷺ وكسرت رباعيته، وهشمت البيضة على رأسه، فكانت فاطمة بنت رسول الله ﷺ تغسل الدم، وكان علي بن أبي طالب يسكب عليها بالمجن، فلما رأت فاطمة أن الماء لا يزيد الدم إلاكثرة، أخذت قطعة حصير، فأحرقته حتى صار رمادا، ثم ألصقته بالجرح فاستمسك الدم.
Bukhari narrated it in the Book of Jihad and Expeditions (2911), and Muslim in the Book of Jihad and Expeditions (101:1790), both through the route of Abdul-Aziz bin Abu Hazim, from his father, that he heard Sahl bin Saad being asked about the wound of the Messenger of Allah ﷺ on the day of Uhud, and he said, then he mentioned it.