Sahih Bukhari Volume 4, Book 56, Hadith 2904

حَدَّثَنَا سَعِيدُ بْنُ عُفَيْرٍ، حَدَّثَنَا يَعْقُوبُ بْنُ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي حَازِمٍ، عَنْ سَهْلٍ، قَالَ لَمَّا كُسِرَتْ بَيْضَةُ النَّبِيِّ صلى الله عليه وسلم عَلَى رَأْسِهِ وَأُدْمِيَ وَجْهُهُ، وَكُسِرَتْ رَبَاعِيَتُهُ، وَكَانَ عَلِيٌّ يَخْتَلِفُ بِالْمَاءِ فِي الْمِجَنِّ، وَكَانَتْ فَاطِمَةُ تَغْسِلُهُ، فَلَمَّا رَأَتِ الدَّمَ يَزِيدُ عَلَى الْمَاءِ كَثْرَةً عَمَدَتْ إِلَى حَصِيرٍ، فَأَحْرَقَتْهَا وَأَلْصَقَتْهَا عَلَى جُرْحِهِ، فَرَقَأَ الدَّمُ‏

Narrated By Sahl : When the helmet of the Prophet was smashed on his head and blood covered his face and one of his front teeth got broken, 'Ali brought the water in his shield and Fatima the Prophet's daughter) washed him. But when she saw that the bleeding increased more by the water, she took a mat, burnt it, and placed the ashes on the wound of the Prophet and so the blood stopped oozing out.