General Behavior (Kitab Al-Adab)
43/97. Chapter:
Regarding yawning
Sunan Abi Dawud
حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، حَدَّثَنَا زُهَيْرٌ، عَنْ سُهَيْلٍ، عَنِ ابْنِ أَبِي سَعِيدٍ الْخُدْرِيِّ، عَنْ أَبِيهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا تَثَاءَبَ أَحَدُكُمْ فَلْيُمْسِكْ عَلَى فِيهِ فَإِنَّ الشَّيْطَانَ يَدْخُلُ " .
Abu Sa’id al-Khudri reported the Messenger of Allah (May peace be upon him) as saying: When one of you yawns, he should hold his hand over his mouth, for the devil enters.
Reference : Sunan Abi Dawud 5026In-book reference : Book 43, Hadith 254English translation : Book 42, Hadith 5008