Hadith 17:697
Abu Khalid al-Ahmar narrated to us, from Ibn ‘Ajlan, from Nafi’, from Ibn ‘Umar, that when he would say "Yarhamukum Allah" (May Allah have mercy on you) to one who sneezed, he would say: "May Allah have mercy on us and you." And when he himself sneezed and was told "Yarhamuk Allah" (May Allah have mercy on you), he would say: "May Allah forgive us and you, and have mercy on us and you."
حدثنا أبو خالد الأحمر عن بن عجلان عن نافع عن بن عمر أنه كان إذا شمت العاطس قال يرحمنا الله وإياكم فإذا عطس هو فشمت قال يغفر الله لنا ولكم ويرحمنا وإياكم