آداب العطاس
Covering the mouth and lowering the voice when sneezing, paired with a specific verbal exchange between the sneezer and those nearby.
كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا عَطَسَ وَضَعَ يَدَهُ أَوْ ثَوْبَهُ عَلَى فِيهِ، وَغَضَّ بِهَا صَوْتَهُ
“When the Messenger of Allah ﷺ sneezed, he would place his hand or garment over his mouth and lower his voice with it.” (meaning, not a literal translation)
The well-known verbal exchange — saying 'al-hamdu lillah' and receiving 'yarhamuk Allah' in reply — is separately recorded in Sahih al-Bukhari 6224.
Commentators note the direct respiratory-hygiene value of covering the mouth, alongside the social and spiritual dimension of the reply exchange.