Sunan an-Nasa'i 723
سنن النسائي#723SahihIt was narrated that Anas said:"The Messenger of Allah (ﷺ) said: 'Spitting in the Masjid is a sin, and its expiation is to bury it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 8:36