brightness_1 Resisting yawning as much as possible, or holding the hand over the mouth while yawning.

This is proven by the following Hadeeth:

Abu Hurayrah (ABPWH) narrated that the Prophet (PBUH) said, “Allāh likes sneezing and dislikes yawning, so if someone sneezes and then praises Allāh, it is his right on every Muslim who heard him to answer him, ‘Yarhamuk Allāh’ (i.e. May Allāh have mercy on you). As for yawning, it is from Satan, so one should try his best to stop it. If one says ‘Ha’ while yawning, Satan laughs at him.” (Al-Bukhāriy no. 2663)

Imām Muslim reports through Abi Sa‘eed (ABPWH) that the Prophet (PBUH) said, “When one of you yawns, he should hold his hand over his mouth, lest Satan enters therein.” (Muslim no. 2995)

Thus, one should try to prevent yawning either by repressing it by closing his mouth or biting his lower lip or similar methods, or he should at least cover his mouth with his hand while yawning. In addition, it is preferred for one who yawns to avoid raising his voice while yawning or making sounds like “Ha” or “Ah” or similar sounds, as this makes Satan laugh at him.

This is proven by the following Hadeeth:

Abu Hurayrah (ABPWH) reported that the Prophet (PBUH) said, “Yawning is from Satan. Thus, one who yawns should try his best to stop it, and if one says ‘Ha’ while yawning, Satan laughs at him.’.” (Al-Bukhāriy no. 3298, Muslim no. 2994)

Note: Some people are used to saying { أعوذ بالله من الشيطان الرجيم } “I ask Allāh’s refuge against the cursed devil” after yawning. It should be noted that there is no valid evidence for this and it is not part of the Prophet’s Sunnah, as the Prophet (PBUH) did not say this when he yawned.