When the helmet broke on the head of the Prophet ﷺ and his face became covered with blood and his incisor tooth broke (i.e. during the battle of Uhud), ʿAli used to bring water in his shield while Fatima was washing the blood off his face. When Fatima saw that the bleeding increased because of the water, she took a mat (of palm leaves), burnt it, and stuck it (the burnt ashes) on the wound of Allah's Apostle, whereupon the bleeding stopped.  

لَمَّا كُسِرَتْ عَلَى رَأْسِ رَسُولِ اللَّهِ ﷺ الْبَيْضَةُ وَأُدْمِيَ وَجْهُهُ وَكُسِرَتْ رَبَاعِيَتُهُ وَكَانَ عَلِيٌّ يَخْتَلِفُ بِالْمَاءِ فِي الْمِجَنِّ وَجَاءَتْ فَاطِمَةُ تَغْسِلُ عَنْ وَجْهِهِ الدَّمَ فَلَمَّا رَأَتْ فَاطِمَةُ عَلَيْهَا السَّلاَمُ الدَّمَ يَزِيدُ عَلَى الْمَاءِ كَثْرَةً عَمَدَتْ إِلَى حَصِيرٍ فَأَحْرَقَتْهَا وَأَلْصَقَتْهَا عَلَى جُرْحِ رَسُولِ اللَّهِ ﷺ فَرَقَأَ الدَّمُ