(100) باب كَمْ مَرَّةٍ يُشَمَّتُ الْعَاطِسُ
Narrated AbuHurayrah:
Respond three times to your brother when he sneezes, and if he sneezes more often, he has a cold in his head.
Reference: Sunan Abi Dawud 5034
In-book reference: Book 43, Hadith 262
English translation: Book 42, Hadith 5016