When the Messenger of Allah ﷺ sneezed, he placed his hand or a garment on his mouth, and lessened the noise. The transmitter Yahya is doubtful about the exact words khafada or ghadda (lessened).  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا عَطَسَ وَضَعَ يَدَهُ أَوْ ثَوْبَهُ عَلَى فِيهِ وَخَفَضَ أَوْ غَضَّ بِهَا صَوْتَهُ شَكَّ يَحْيَى  

There are five qualities which a Muslim should display to his brother : return of salutation, response to the one who sneezes, acceptance of the invitation, paying sick visit to a patient, and accompanying the funeral.  

قَالَ رَسُولُ اللَّهِ ﷺ خَمْسٌ تَجِبُ لِلْمُسْلِمِ عَلَى أَخِيهِ رَدُّ السَّلاَمِ وَتَشْمِيتُ الْعَاطِسِ وَإِجَابَةُ الدَّعْوَةِ وَعِيَادَةُ الْمَرِيضِ وَاتِّبَاعُ الْجَنَازَةِ