Sahih Muslim 1227
صحيح مسلم#1227SahihA'isha reported:The Apostle of Allah (may, peace be upon him) saw spittle or snot or sputum, sticking to the wall towards Qibla and scratched it off
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 5:65