Abu Saeed Al-Khudri reported the Messenger of Allah ﷺ as saying: When one of you yawns, he should hold his hand over his mouth, for the devil enters.
Related hadith on this topic
Explanation & Benefits
Shaykh Maulana Abdul Aziz Alvi
Hadith Commentary:
Benefits and Issues:
➊ In general circumstances, when one feels like yawning, one should try to restrain it.
➋ However, in the state of prayer, this emphasis is even greater.
Source: Tuhfat al-Muslim: Commentary on Sahih Muslim, Page: 7493