(9) باب تَشْمِيتِ الْعَاطِسِ وَكَرَاهَةِ التَّثَاؤُبِ
The son of Abu Said al-Khudri reported on the authority of his father that Allah's Messenger (ﷺ) said. When one of you yawns while engaged in prayer, he should try to restrain so far as it lies in his power, since it is the Satan that enter therein.
Reference: Sahih Muslim 2995 c
In-book reference: Book 55, Hadith 76
USC-MSA web (English) reference(deprecated numbering scheme): Book 42, Hadith 7132