I was traveling with Salim bin Ubayd when a man sneezed and said, "Peace be upon you."Salim replied, "Upon you and upon your mother."Then they went on, and Salim said, "Perhaps you took offense at that?"The man said, "I wished you had not mentioned my mother."Salim said, "I could not say anything but that. I was traveling with the Messenger of Allah ﷺ when a man sneezed and said, 'Peace be upon you,' and he replied, 'Upon you and upon your mother.' Then he said, 'When one of you sneezes, let him say, "Praise be to Allah in every circumstance," or "Praise be to Allah, Lord of the worlds." And let the one beside him say, "May Allah have mercy on you all," or "May Allah have mercy on you," ' " Yahya being uncertain which, " 'and let him say, "May Allah forgive me and you." ' "
حدثنا يحيى بن سعيد حدثني سفيان حدثنا منصور عن هلال بن يساف
كنت مع سالم بن عبيد في سفر فعطس رجل فقال السلام عليكم فقال عليك وعلى أمك ثم سار فقال لعلك وجدت في نفسك قال ما أردت أن تذكر أمي قال لم أستطع إلا أن أقولها كنت مع رسول الله ﷺ في سفر فعطس رجل فقال السلام عليك فقال عليك وعلى أمك ثم قال إذا عطس أحدكم فليقل الحمد لله على كل حال أو الحمد لله رب العالمين وليقل له يرحمكم الله أو يرحمك الله شك يحيى وليقل يغفر الله لي ولكم
Its isnad is daif, due to the anonymity of the narrator from Salim bin Ubayd. The hadith is sahih according to the compilers of the Sunan, via the route of Hilal bin Yasaf from Salim bin Ubayd without an intermediary. See Sunan Abu Dawud 4/307, no. 5031 and 5032, and Tirmidhi 5/28, no. 2740, where he made no comment on it, and Nasai in Amal al-Yawm wal-Layla, no. 229.