Sunan an-Nasai 15986
In-book no 1250أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنِ ابْنِ جُرَيْجٍ، قَالَ قَالَ عَبْدُ اللَّهِ بْنُ مُسَافِعٍ عَنْ عُتْبَةَ بْنِ مُحَمَّدِ بْنِ الْحَارِثِ، عَنْ عَبْدِ اللَّهِ بْنِ جَعْفَرٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ شَكَّ فِي صَلاَتِهِ فَلْيَسْجُدْ سَجْدَتَيْنِ بَعْدَ مَا يُسَلِّمُ " .
It was narrated that Abdullah bin Ja'far said: "The Messenger of Allah (ﷺ) said: 'Whoever has doubt during his prayer, let him prostrate twice after he has said the taslim'".