حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي دَاوُدَ ، ثنا أَبُو سَعِيدٍ الأَشَجُّ ، ثنا أَبُو خَالِدٍ ، عَنْ مُحَمَّدِ بْنِ عَجْلانَ ، عَنْ زَيْدِ بْنِ أَسْلَمَ ، عَنْ عَطَاءِ بْنِ يَسَارٍ ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ ، قَالَ : قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " إِذَا شَكَّ أَحَدُكُمْ فِي صَلاتِهِ فَلْيُلْقِ الشَّكَّ وَلْيَبْنِ عَلَى الْيَقِينِ ، فَإِنِ اسْتَيْقَنَ التَّمَامَ سَجَدَ سَجْدَتَيْنِ ، فَإِنْ كَانَتْ صَلاتُهُ تَامَّةً كَانَتِ الرَّكْعَةُ نَافِلَةً وَالسَّجْدَتَانِ ، وَإِنْ كَانَتْ نَاقِصَةً كَانَتِ الرَّكْعَةُ تَمَامًا لِصَلاتِهِ وَالسَّجْدَتَانِ تُرْغِمَانِ أَنْفَ الشَّيْطَانِ " .
Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) said: "When a person has doubt about his prayer, he should put aside the doubt and base (his action) on what is certain, and when he has certainly completed the prayer (then at the end) he should perform two prostrations of forgetfulness. If his prayer was complete, then the extra rak‘ah and two prostrations will be counted as voluntary for him, and if his prayer was incomplete before, then through that one rak‘ah his prayer will be completed, and both prostrations of forgetfulness will rub the nose of Satan in the dust."