It was narrated from Ali that the Messenger of Allah(ﷺ) said: "If anyone of you sneezes, let him say: Alhamdulillah (praise be to Allah). Those around him should respond by saying: Yarhamkullah (may Allah have mercy on you). And he should respond by saying: "Yahdikum Allah wa yuslaha balakum (may Allah Guide you and set right your state)."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنِ ابْنِ أَبِي لَيْلَى، عَنْ عِيسَى، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي لَيْلَى، عَنْ عَلِيٍّ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ " إِذَا عَطَسَ أَحَدُكُمْ فَلْيَقُلِ الْحَمْدُ لِلَّهِ . وَلْيَرُدَّ عَلَيْهِ مَنْ حَوْلَهُ يَرْحَمُكَ اللَّهُ . وَلْيَرُدَّ عَلَيْهِمْ يَهْدِيكُمُ اللَّهُ وَيُصْلِحُ بَالَكُمْ " .
sunnah.com