Malik related to me from Nafi that when Abdullah ibn Umar sneezed and someone said to him, "May Allah have mercy on you," (Yarhamuka'llah), he said, "May Allah have mercy on us and you, and forgive us and you." (Yarhamuna'llah wa yaghfirlana wa lakum).  

أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ كَانَ إِذَا عَطَسَ فَقِيلَ لَهُ يَرْحَمُكَ اللَّهُ قَالَ يَرْحَمُنَا اللَّهُ وَإِيَّاكُمْ وَيَغْفِرُ لَنَا وَلَكُمْ  

The Messenger of Allah ﷺ said: “If one of you sneezes, let him say, Praise be to Allah the Lord of the Worlds, and let those who are around him say: May Allah have mercy on you, and let him say, May Allah guide you and rectify your condition.” (Using translation from Aḥmad 972)   

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا عَطَسَ أَحَدُكُمْ فَلْيَقُلِ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ وَلْيُقَلْ لَهُ يَرْحَمُكَ اللَّهُ وَلْيَقُلْ يَغْفِرُ اللَّهُ لَنَا وَلَكُمْ  

[Machine] The Messenger of Allah ﷺ used to teach us that when one of you sneezes, they should say, "Alhamdulillah, Lord of the worlds." And when they say that, they should also say, "May Allah have mercy on you." And when they say that, they should also say, "May Allah forgive me and you."  

كَانَ رَسُولُ اللهِ ﷺ يُعَلِّمُنَا إِذَا عَطَسَ أَحَدُكُمْ فَلْيَقُلِ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ فَإِذَا قَالَ ذَلِكَ فَلْيَقُلْ مَنْ عِنْدَهُ يَرْحَمُكَ اللهُ فَإِذَا قَالَ فَلْيَقُلْ يَغْفِرُ اللهُ لِي وَلَكُمْ