"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.'"  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا نَعَسَ الرَّجُلُ وَهُوَ فِي الصَّلاَةِ فَلْيَنْصَرِفْ لَعَلَّهُ يَدْعُو عَلَى نَفْسِهِ وَهُوَ لاَ يَدْرِي