The Prophet ﷺ said, "When one of you sneezes, let him say, 'Praise be to Allah,' and let his brother or companion say to him, 'May Allah have mercy on you.' When he says to him, 'May Allah have mercy on you,' let him reply, 'May Allah guide you and set your affairs right.'"
عن النبي ﷺ قال: إذا عطس أحدكم فليقل: الحمد لله، وليقل له أخوه أو صاحبه: يرحمك الله، فإذا قال له: يرحمك الله، فليقل: يهديكم الله ويصلح بالكم.
Bukhari narrated it in Al-Adab (6224) from Malik bin Ismail, who said, Abdul-Aziz bin Abu Salama narrated to us, Abdullah bin Dinar informed us, from Abu Salih, from Abu Hurairah, and he mentioned it.Similar in meaning is what was narrated from Ali, who said, the Messenger of Allah ﷺ said, "When one of you sneezes, let him say, 'Praise be to Allah.' And let those around him respond, 'May Allah have mercy on you.' And let him respond to them, 'May Allah guide you and set your affairs right.'" Tirmidhi narrated it (2741/2), and Ibn Majah (3715) - and this is his wording, and Ahmad (995), and Nasai in Amal al-Yawm wal-Layla (212), and Hakim (4/266), all of them through routes from Muhammad bin Abdul-Rahman bin Abu Layla, from his brother Isa, from his father Abdul-Rahman bin Abu Layla, and he mentioned it.Tirmidhi also narrated it (2741), and Ahmad (23557), and Nasai in Amal al-Yawm wal-Layla (213), and Hakim (4/266), all of them through the route of Shubah, from Ibn Abu Layla, from his brother Isa, from Abdul-Rahman bin Abu Layla, from Abu Ayub, from the Prophet ﷺ, with similar wording.Muhammad bin Abdul-Rahman bin Abu Layla had a poor memory, and he was inconsistent in this hadith, and this is the defect that Tirmidhi, Nasai, and Hakim attributed it to.