Al-Nawawī said: If someone spits inside a mosque, he has committed something unlawful and must bury it; anyone who sees another person spit in the mosque is obliged to reprimand him.

10 – Islam advocates cleanliness, purity, and propriety, and it strongly dissuades from filth and grime. It is therefore preferable for a Muslim to carry tissues with him so that he can remove any dirt or harm and then discard them in the proper trash containers and locations.