Sayyiduna Sa’d bin Abi Waqqas (may Allah be pleased with him) narrates that I heard the Messenger of Allah (peace and blessings be upon him) say: When any of you spits or clears his throat in the mosque, he should conceal it, lest it may fall on the body or clothes of a believer and cause him harm.
Hadith Referenceالفتح الربانی / أبواب المساجد / 1340