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.
The Book of Zuhd and Softening of Hearts - Sahih Muslim 2995 a
In the name of Allah, the Most Gracious, the Most Merciful. This narration from Sahih Muslim's "Book of Zuhd and Softening of Hearts" addresses the proper etiquette when yawning, as taught by the Prophet Muhammad (peace be upon him).
Scholarly Commentary on Yawning Etiquette
The classical scholars explain that yawning originates from satiety and laziness, which stem from the self (nafs) that inclines toward evil. When a person feels drowsy or lazy, the devil finds an opportunity to mock and distract the believer.
Imam An-Nawawi, in his commentary on Sahih Muslim, states that covering the mouth during yawning is recommended (mustahabb) because the devil delights in the open mouth and may enter or cause harm. The hand serves as a barrier against this spiritual harm.
Scholars emphasize that this teaching combines both physical etiquette and spiritual protection. The act of covering one's mouth demonstrates mindfulness of Allah even in involuntary actions and protects against the devil's influence during moments of weakness.
Practical Implementation
The majority of scholars hold that one should cover the mouth with the back of the hand or palm when yawning. Some recommend saying "A'udhu billahi minash-shaytanir-rajim" (I seek refuge with Allah from Satan, the accursed) when feeling a yawn approaching.
This teaching reminds believers that Islamic guidance encompasses all aspects of life, including natural bodily functions, transforming them into acts of worship through proper intention and adherence to prophetic example.