Messenger of Allah ﷺ saw some expectoration on the wall of the mosque; he took gravel and scraped it off and said, "If anyone of you wanted to spit he should neither spit in front of him nor on his right but he could spit either on his left or under his left foot." (Using translation from Bukhārī 408)
"إذَا تنخَّمَ أحدُكمْ فلا يتنخَّمنَّ قِبَل وَجْهِه ولا عنْ يمينه وليبصُقْ عن يساره أو تحت قدمِه اليُسْرى".