Imam Bukhari narrates: 'Abdullah bin Yusuf narrated to us the hadeeth, he said: Imam Malik informed us, from Hisham bin 'Urwah, from his father, from Hazrat 'Ayeshah, Mother of the Believers (may Allāh be pleased with her)

that the Messenger of Allāh ﷺ saw mucus (moisture of the nose) or spit or phlegm on the wall of the Qiblah, so he scraped it and cleaned it.