The Jews used to sneeze in the presence of the Prophet ﷺ hoping he would say to them, "May Allah have mercy on you." Instead, he would say, "May Allah guide you and set your affairs right."
حدثنا عثمان بن أبي شيبة حدثنا وكيع حدثنا سفيان عن حكيم بن الديلم
كانت اليهود تعاطس عند النبي ﷺ رجاء أن يقول لها يرحمكم الله فكان يقول يهديكم الله ويصلح بالكم
Its isnad is sahih. Tirmidhi transmitted it in the Book of Manners, in the chapter on how to respond to one who sneezes, hadith no. 2739, from the hadith of Sufyan Thawri, with this wording, and he said, hasan sahih. Sufyan explicitly stated the continuous chain of hearing (musalsal) with Hakim, 4/268.