(13) باب النَّهْىِ عَنِ الْبُصَاقِ، فِي الْمَسْجِدِ فِي الصَّلاَةِ وَغَيْرِهَا
'Abdullah b. Shakhkhir narrated it on the authority of his father that he said prayer with the Messenger of Allah (ﷺ), and he spat and then rubbed it off with his left shoe.
Reference: Sahih Muslim 554 b
In-book reference: Book 5, Hadith 73
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1128