Yahya related to me from Malik from Hisham ibn Urwa from hisfather from A'isha, the wife of the Prophet, mayAllah bless him andgrant him peace, that the Prophet, may Allah bless him and grant himpeace, saw spittle, or mucus or phlegm, on the wall of the qibla andscraped it off.
USC-MSA web (English) reference: Book 14, Hadith 5
Arabic reference: Book 14, Hadith 462