Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that when the Messenger of Allah (peace and blessings be upon him) sneezed, "he would place his hand or his garment over his blessed mouth and sneeze with a lowered voice."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3580