Musannaf Ibn Abi Shayba 3:5098

Abu Bakr narrated to us, he said: Abdullah ibn Numayr narrated to us, he said: Muhammad ibn Ishaq narrated to us, from Abdullah ibn Muhammad, from Amir ibn Sa’d ibn Abi Waqqas, from his father Sa’d, he said: I heard the Prophet, may Allah bless him and grant him peace, saying: "If one of you clears his throat in the mosque, let him hide it (let him cover it), so that it does not touch the skin of a believer or his garment and harm him."