It was narrated that Aishah said:
"The Messenger of Allah (ﷺ) said: 'If a man feels drowsy when he is praying, let him stop, lest he supplicate against himself without realizing.'" (JA)
English reference (JA): Vol. 1, Book 1, Hadith 162 (JA)
Arabic reference (JA): Book 1, Hadith 163 (JA)