Riyad as-SalihinChapter 5Hadith 201
Full Sharh — Riyad as-Salihin 201
وعن أبي موسي رضي الله عنه قال: سمعت رسول الله صلى الله عليه وسلم يقول: "إذا عطس أحدكم فحمد الله فشمتوه، فإن لم يحمد الله فلا تشمتوه" ((رواه مسلم)).
English Translation
Abu Musa (May Allah be pleased with him) reported:: The Messenger of Allah (ﷺ) said, "When one of you sneezes and praises Allah (i.e., says Al-hamdu lillah), you should invoke Allah's Mercy upon him (i.e., say Yarhamuk-Allah); but if he does not praise Allah, you should not respond." .
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Greetings
Hadith Number
201