Sahih
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا الأَعْمَشُ، عَنْ إِبْرَاهِيمَ، عَنْ عَلْقَمَةَ، عَنْ عَبْدِ اللَّهِ، بِهَذَا قَالَ " فَإِذَا نَسِيَ أَحَدُكُمْ فَلْيَسْجُدْ سَجْدَتَيْنِ " . ثُمَّ تَحَوَّلَ فَسَجَدَ سَجْدَتَيْنِ . قَالَ أَبُو دَاوُدَ رَوَاهُ حُصَيْنٌ نَحْوَ حَدِيثِ الأَعْمَشِ .
This tradition has also been transmitted by ‘Abd Allah (b. Mas’ud) through a different chain of narrators. This version goes; when one of you forgets (in his prayer), he should perform two prostrations. Then he turned away, and performed two prostrations (due to forgetfulness). Abu Dawud said:The narrator Husain also reported it like al-A'mash