Abu Hurairah (May Allah be pleased with him) reported:
The Prophet (ﷺ) said, "Allah likes sneezing and dislikes yawning. When any one of you sneezes and says `Al-hamdu lillah (praise be to Allah)', it becomes obligatory upon every Muslim who hears him to respond with `Yarhamuk-Allah (may Allah have mercy on you)'. Yawning is from the devil. When one of you feels like yawning, he should restrain it as much as possible, for the devil laughs when one of you yawns."
[Al-Bukhari].