Riyad as-SalihinChapter 5Hadith 200
Full Sharh — Riyad as-Salihin 200
وعنه عن النبي صلى الله عليه وسلم الله قال: "إذا عطس أحدكم فليقل: الحمد لله؛ وليقل له أخوه أو أصحابه: يرحمك الله، فإذا قال له: يرحمك الله، فليقل: يهديكم الله ويصلح بالكم" ((رواه البخاري)).
English Translation
Abu Hurairah (May Allah be pleased with him) reported:: The Prophet (ﷺ) said, "When one of you sneezes he should say: 'Al-hamdu lillah (praise be to Allah),' and his brother or his companion should say to him: 'Yarhamuk-Allah (may Allah have mercy on you).' When he says this he should reply: 'Yahdikum-ullah wa yuslihu balakum (may Allah guide you and render sound your state of affairs)."'.
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Greetings
Hadith Number
200