حَدَّثَنِي أَبُو غَسَّانَ الْمِسْمَعِيُّ، مَالِكُ بْنُ عَبْدِ الْوَاحِدِ حَدَّثَنَا بِشْرُ بْنُ الْمُفَضَّلِ، حَدَّثَنَا سُهَيْلُ بْنُ أَبِي صَالِحٍ، قَالَ سَمِعْتُ ابْنًا، لأَبِي سَعِيدٍ الْخُدْرِيِّ يُحَدِّثُ أَبِي عَنْ أَبِيهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا تَثَاوَبَ أَحَدُكُمْ فَلْيُمْسِكْ بِيَدِهِ عَلَى فِيهِ فَإِنَّ الشَّيْطَانَ يَدْخُلُ " .
The son of Abu Said al-Khudri reported on the authority of his father that Allah's Messenger (PBUH) said: When one of you yawns, he should keep his mouth shut with the help of his hand, for it is the devil that enters therein. Translation Not Available
Book Ref: Sahih Muslim Book 55 Hadith 7130
Web Ref: Sahih Muslim Book 42 Hadith 2995 a