“The Satan comes between the son of Adam and his soul, and he does not know how many Rak’ah he has prayed. If a person notices that, then let him prostrate twice before he says the Salam.”
أَنَّ النَّبِيَّ ﷺ قَالَ إِنَّ الشَّيْطَانَ يَدْخُلُ بَيْنَ ابْنِ آدَمَ وَبَيْنَ نَفْسِهِ فَلاَ يَدْرِي كَمْ صَلَّى فَإِذَا وَجَدَ ذَلِكَ فَلْيَسْجُدْ سَجْدَتَيْنِ قَبْلَ أَنْ يُسَلِّمَ