Reference: al-Fataawa al-Muhimmah p701
Liqaa.aat al-Baab al-Maftooh no.1059
Question: Is there anything [authentically reported] from the Messenger ﷺ that we should say "shafaa-kAllaah" (شفاك الله) to the one who sneezes a third time?
Response: Yes. If someone sneezes and says:
"al-Hamdu-lillaah" (الحمد لله), [then] say to him:
"yarhamu-kAllaah" (يرحمك الله).
And if he sneezes a second [time] and says:
"al-Hamdu-lillaah" (الحمد لله), [then] say to him:
"yarhamu-kAllaah" (يرحمك الله).
And if he sneezes a third [time] and says:
"al-Hamdu-lillaah" (الحمد لله), [then] say to him:
"'aafaa-kAllaah, innaka mazkoom" (عافاك الله، إنك مزكوم), because of the hadeeth of Salamah ibn al-Akwa' [transmitted by Muslim no.2993].
Likewise, pray for his well being.
