Bless your brother when he sneezes three times. Anything beyond that is a cold.
حدثنا مسدد حدثنا يحيى عن ابن عجلان قال حدثني سعيد بن أبي سعيد
شمت أخاك ثلاثا فما زاد فهو زكام
No references are available.
[Its isnad is hasan] Bukhari narrated it in Adab al-Mufrad, no. 935, from the hadith of Muhammad bin Ajlan through this route.