Hadith 17:681
Jarir ibn Abd al-Hamid narrated to us, from Mughira, from al-Sha'bi, who said: Amr ibn al-Aas said: "If one of you sneezes three times, then say 'Yarhamuk Allah' (may Allah have mercy on you) to him. But if he exceeds that, do not say it to him, for it is only an ailment coming out of his head."
حدثنا جرير بن عبد الحميد عن مغيرة عن الشعبي قال قال عمرو بن العاص إذا عطس أحدكم ثلاث مرات فشمتوه وإن زاد فلا تشمتوه فإنما هو داء يخرج من رأسه