“I heard the Messenger of Allah ﷺ say: ‘If anyone of you is uncertain as to whether he has prayed one or two Rak’ah, let him assume it is one. If he is uncertain as to whether he has prayed two or three, let him assume it is two. If he is uncertain as to whether he has prayed three or four, let him assume it is three. Then let him complete what is left of his prayer, so that the doubt will be about what is more. Then let him prostrate twice while he is sitting, before the Taslim (saying the Salam).’”  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِذَا شَكَّ أَحَدُكُمْ فِي الثِّنْتَيْنِ وَالْوَاحِدَةِ فَلْيَجْعَلْهَا وَاحِدَةً وَإِذَا شَكَّ فِي الثِّنْتَيْنِ وَالثَّلاَثِ فَلْيَجْعَلْهَا ثِنْتَيْنِ وَإِذَا شَكَّ فِي الثَّلاَثِ وَالأَرْبَعِ فَلْيَجْعَلْهَا ثَلاَثًا ثُمَّ لْيُتِمَّ مَا بَقِيَ مِنْ صَلاَتِهِ حَتَّى يَكُونَ الْوَهْمُ فِي الزِّيَادَةِ ثُمَّ يَسْجُدْ سَجْدَتَيْنِ وَهُوَ جَالِسٌ قَبْلَ أَنْ يُسَلِّمَ  

“The Messenger of Allah ﷺ said: ‘If anyone of you is uncertain about his prayer, let him put aside uncertainty and act upon that which is certain. When he has made sure his prayer is complete, then let him prostrate twice. Then if his prayer was complete, that (extra) Rak’ah will be counted as voluntary, and if his prayer was lacking, that Rak’ah will complete his prayer, and the two prostrations will rub the Satan’s nose in the dust.’”  

قَالَ رَسُولُ اللَّهِ ﷺ إِذَا شَكَّ أَحَدُكُمْ فِي صَلاَتِهِ فَلْيُلْغِ الشَّكَّ وَلْيَبْنِ عَلَى الْيَقِينِ فَإِذَا اسْتَيْقَنَ التَّمَامَ سَجَدَ سَجْدَتَيْنِ فَإِنْ كَانَتْ صَلاَتُهُ تَامَّةً كَانَتِ الرَّكْعَةُ نَافِلَةً وَإِنْ كَانَتْ نَاقِصَةً كَانَتِ الرَّكْعَةُ لِتَمَامِ صَلاَتِهِ وَكَانَتِ السَّجْدَتَانِ رَغْمَ أَنْفِ الشَّيْطَانِ