Sahih Bukhari Volume 001, Book 004, Hadith Number 244.
Narated By Abu Hazim : Sahl bin Sa'd As-Sa'idi, was asked by the people, "With what was the wound of the Prophet treated? Sahl replied, "None remains among the people living who knows that better than I. 'Ah used to bring water in his shield and Fatima used to wash the blood off his face. Then straw mat was burnt and the wound was filled with it."