It was narrated that 'Abdullah said:

"The Messenger of Allah ﷺ said: 'If one of you is not sure about his prayer, let him estimate and prostrate twice after he has finished."

أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ الْمُخَرَّمِيُّ، قَالَ حَدَّثَنَا وَكِيعٌ، عَنْ مِسْعَرٍ، عَنْ مَنْصُورٍ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ، قَالَ قَالَ رَسُولُ اللَّهِ ﷺ " إِذَا شَكَّ أَحَدُكُمْ فِي صَلاَتِهِ فَلْيَتَحَرَّ وَيَسْجُدْ سَجْدَتَيْنِ بَعْدَ مَا يَفْرُغُ " .