Sahih al-Bukhari 78:248
Narrated Abu Huraira:
The Prophet (ﷺ) said, " If anyone of you sneezes, he should say 'Al-Hamduli l-lah' (Praise be to Allah), and his (Muslim) brother or companion should say to him, 'Yar-hamuka-l-lah' (May Allah bestow his Mercy on you). When the latter says 'Yar-hamuka-llah", the former should say, 'Yahdikumul-lah wa Yuslih balakum' (May Allah give you guidance and improve your condition).
Reference
Sahih al-Bukhari 78:248
In-book reference
Book 78, Hadith 248
Arabic Text
حَدَّثَنَا مَالِكُ بْنُ إِسْمَاعِيلَ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ أَبِي سَلَمَةَ، أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ دِينَارٍ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِذَا عَطَسَ أَحَدُكُمْ فَلْيَقُلِ الْحَمْدُ لِلَّهِ. وَلْيَقُلْ لَهُ أَخُوهُ أَوْ صَاحِبُهُ يَرْحَمُكَ اللَّهُ. فَإِذَا قَالَ لَهُ يَرْحَمُكَ اللَّهُ. فَلْيَقُلْ يَهْدِيكُمُ اللَّهُ وَيُصْلِحُ بَالَكُمْ ".