The Prophet ﷺ said, "When one of you sneezes, let him say, 'Praise be to Allah.' When he says, 'Praise be to Allah,' his brother should say to him, 'May Allah have mercy on you.' And when he is told, 'May Allah have mercy on you,' let him reply, 'May Allah guide you and set your affairs right.'"
حدثنا حجين أبو عمر حدثنا عبد العزيز عن عبد الله بن دينار عن أبي صالح السمان
عن النبي ﷺ قال إذا عطس أحدكم فليقل الحمد لله فإذا قال الحمد لله قال له أخوه يرحمك الله فإذا قيل له يرحمك الله فليقل يهديكم الله ويصلح بالكم
Suyuti narrated it with the wording, "When one of you sneezes, let him say, 'Praise be to Allah, Lord of the worlds,' and let the other say to him, 'May Allah have mercy on you,' and let him say, 'May Allah forgive us and you.'"Tabarani narrated it in Al-Kabir, and Hakim, and Bayhaqi in Shuab al-Iman, from Ibn Masud.Abu Dawud, Tirmidhi, Nasai, and Hakim, and Bayhaqi in Shuab al-Iman, narrated it from Salim bin Ubayd Ashjai.Suyuti indicated in Al-Jami al-Saghir that it is sahih.