Nafi' said that when 'Abdullah ibn 'Umar sneezed, they said to him, "May Allah have mercy on you," and Ibn 'Umar said, "May He have mercy on us and you. May He forgive us and you."  

أَنَّهُ كَانَ إِذَا عَطَسَ فَقِيلَ لَهُ يَرْحَمُكَ اللَّهُ فَقَالَ يَرْحَمُنَا اللَّهُ وَإِيَّاكُمْ وَيَغْفِرُ لَنَا وَلَكُمْ  

'Abdullah said, "When one of you sneezes, he should say, 'Praise be to Allah, the Lord of the Worlds.' Let anyone responding to him say 'May Allah have mercy on you.' Then the person who sneezed should say'May Allah forgive me and you.'"  

عَنْ عَبْدِ اللهِ قَالَ إِذَا عَطَسَ أَحَدُكُمْ فَلْيَقُلِ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ وَلْيَقُلْ مَنْ يَرُدُّ يَرْحَمُكَ اللَّهُ وَلْيَقُلْ هُوَ يَغْفِرُ اللَّهُ لِي وَلَكُمْ  

Iyas ibn Salama related that his father said, "A man sneezed in the presence of the Prophet, may Allah bless him and grant him peace, and the Prophet said, 'May Allah have mercy on you.' Then the man sneezed again and the Prophet, may Allah bless him and grant him peace, said, 'This man has a cold.'"  

عَنْ أَبِيهِ قَالَ عَطَسَ رَجُلٌ عِنْدَ النَّبِيِّ ﷺ فَقَالَ يَرْحَمُكَ اللَّهُ ثُمَّ عَطَسَ أُخْرَى فَقَالَ النَّبِيُّ ﷺ هَذَا مَزْكُومٌ