(the mother of faithful believers) Messenger of Allah ﷺ saw some nasal secretions, expectoration or sputum on the wall of the mosque in the direction of the Qibla and scraped it off.  

أَنَّ رَسُولَ اللَّهِ ﷺ رَأَى فِي جِدَارِ الْقِبْلَةِ مُخَاطًا أَوْ بُصَاقًا أَوْ نُخَامَةً فَحَكَّهُ