Prophet said, "If anyone of you stands for prayer, he should not spit in front of him because in prayer he is speaking in private to Allah and he should not spit on his right as there is an angel, but he can spit either on his left or under his left foot and bury it (i.e. expectoration).
Sahih al-Bukhari Book 8, Hadith 66
← Previous Hadith The Prophet (ﷺ) said, "Spitting in the mosque is a sin and its expiation is to bury it."

Sahih al-Bukhari Book 8, Hadith 65 Next Hadith → The Prophet (ﷺ) saw expectoration (on the wall of the mosque) in the direction of the Qibla and scraped it off with his hand. It seemed that he disliked it and the sign of disgust was apparent from his face. He said, "If anyone of you stands for the prayer, he is speaking in private to his Lord, (or) his Lord is between him and his Qibla, therefore he should not spit towards his Qibla, but he could spit either on his left or under his foot." Then he took the corner of his sheet and spat in it, folded it and said, "Or do this."

Sahih al-Bukhari Book 8, Hadith 67