Restraining yawning – The Permanent Committee

Q 3: I heard a man saying that when he yawns, he covers his mouth so that Satan may not enter inside him. He attributed this to the Prophet (peace be upon him) and claimed that it was mentioned in the Sahih (authentic) Book of Muslim. Is this true? 

A: It is Mustahab (desirable) for those who yawn to restrain it as much as possible and cover their mouths. The Prophet (peace be upon him) said,

When one of you yawns, you should try to restrain it with the help of your hand, since it is Satan that enters therein. Narrated by Muslim.

In another narration, You should cover your mouth with your hand and not yawn in a loud voice, as Satan will laugh at you if you do so.  

May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.

The Permanent Committee for Scholarly Research and Ifta’
 http://alifta.com/Fatawa/FatawaChapters.aspx?languagename=en&View=Page&PageID=10375&PageNo=1&BookID=7