Narrated Anas bin Malik:

Two men sneezed before the Prophet. The Prophet ﷺ said to one of them, "May Allah bestow His Mercy on you," but he did not say that to the other. On being asked (why), the Prophet ﷺ said, "That one praised Allah (at the time of sneezing), while the other did not praise Allah."

حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، حَدَّثَنَا سُفْيَانُ، حَدَّثَنَا سُلَيْمَانُ، عَنْ أَنَسِ بْنِ مَالِكٍ ـ رضى الله عنه ـ قَالَ عَطَسَ رَجُلاَنِ عِنْدَ النَّبِيِّ ﷺ فَشَمَّتَ أَحَدَهُمَا وَلَمْ يُشَمِّتِ الآخَرَ، فَقِيلَ لَهُ فَقَالَ " هَذَا حَمِدَ اللَّهَ، وَهَذَا لَمْ يَحْمَدِ اللَّهَ ".