Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
nasai-kubra:586 – Muḥammad b. Bashhār > Muḥammad b. Jaʿfar Ghundar > Shuʿbah > al-Ḥakam > Abū Wāʾil > ʿAbdullāh

"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." (Using translation from Nasāʾī 1241)   

الكبرى للنسائي:٥٨٦ – أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ غُنْدَرٌ قَالَ حَدَّثَنَا شُعْبَةُ عَنِ الْحَكَمِ قَالَ سَمِعْتُ أَبَا وَائِلٍ يُحَدِّثُ عَنْ عَبْدِ اللهِ قَالَ

«إِذَا وَهِمْ أَحَدُكُمْ فِي صَلَاتِهِ فَلْيَتَحَرَّ الصَّوَابَ وَيَسْجُدُ سَجْدَتَيْنِ وَهُوَ قَاعِدٌ بَعْدَمَا يُفْرِغُ»  

See similar narrations below:

Collected by Nasāʾī, Nasāʾī's Kubrá
nasai:1241 – Muḥammad b. ʿAbdullāh b. al-Mubārak al-Mukharramī > Wakīʿ > Misʿar > Manṣūr > Ibrāhīm > ʿAlqamah > ʿAbdullāh

"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."  

النسائي:١٢٤١ – 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  

nasai:1245 – Sūwayd b. Naṣr > ʿAbdullāh > Shuʿbah > al-Ḥakam > Abū Wāʾil

"Whoever us not sure about his prayer, then let him estimate what is correct, then let him prostrate twice after he finished his prayer, while he is sitting."  

النسائي:١٢٤٥ – أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ عَنْ شُعْبَةَ عَنِ الْحَكَمِ قَالَ سَمِعْتُ أَبَا وَائِلٍ يَقُولُ قَالَ

عَبْدُ اللَّهِ مَنْ أَوْهَمَ فِي صَلاَتِهِ فَلْيَتَحَرَّ الصَّوَابَ ثُمَّ يَسْجُدْ سَجْدَتَيْنِ بَعْدَ مَا يَفْرُغُ وَهُوَ جَالِسٌ  

nasai-kubra:1165 – Muḥammad b. ʿAbdullāh b. al-Mubārak al-Makhramī > Wakīʿ > Misʿar > Manṣūr > Ibrāhīm > ʿAlqamah > ʿAbdullāh

"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." (Using translation from Nasāʾī 1241)  

الكبرى للنسائي:١١٦٥ – أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللهِ بْنِ الْمُبَارَكِ الْمَخْرَمِيُّ قَالَ حَدَّثَنَا وَكِيعٌ عَنْ مِسْعَرٍ عَنْ مَنْصُورٍ عَنْ إِبْرَاهِيمَ عَنْ عَلْقَمَةَ عَنْ عَبْدِ اللهِ قَالَ

قَالَ رَسُولُ اللهِ ﷺ «إِذَا شَكَّ أَحَدُكُمْ فِي صَلَاتِهِ فَلْيَتَحَرَّ وَلْيَسْجُدْ سَجْدَتَيْنِ بَعْدَمَا يَفْرُغُ»