‏الزهد والرقائق‏ : Hadeeth No:7130 The son of Abu Said al-Khudri reported on the authority of his father that Allaah's Messenger (sallAllaahu alayhi wa sallam) 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....

‏البر والصلة والآداب‏ : Hadeeth No:6241 'A'isha reported: I heard Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: There is nothing (in the form of trouble) that comes to a believer even if it is the pricking of a thorn that there is decreed for him by Allaah good or his sins are obliterated....