The son of Abu Said al-Khudri reported on the authority of his father that Messenger of Allah 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. (Using translation from Muslim 2995c)
قَالَ رَسُولُ اللهِ ﷺ إِذَا تَثَاءَبَ أَحَدُكُمْ فِي الصَّلَاةِ فَلْيَكْظِمْ مَا اسْتَطَاعَ فَإِنَّ الشَّيْطَانَ يَدْخُلُ فِي فِيهِ