When yawning, it is Sunnat to prevent it as far as possible. (Bukhari). If the mouth cannot be kept closed despite making an effort to do so, then place the back of the left hand over the mouth. While yawning, any sound should not be allowed to emanate as this is forbidden in the hadith. (Bukhar‐Vol.2, pg.919, Muslim‐Vol.2, pg. 412, 413)
