´It was narrated from Abu Sa'eed Al-Khudri that the Prophet (ﷺ) saw some spittle in the Qiblah of the Masjid. He scratched it off with a pebble and forbade a man to spit to his front or to his right. He said:` "Let him spit to his left or beneath his left foot."
Hadith Referenceسنن نسائي / كتاب المساجد / 726
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه