Sunan an-Nasa'i 1235
سنن النسائي#1235Sahihأَخْبَرَنَا عَمْرُو بْنُ عُثْمَانَ بْنِ سَعِيدِ بْنِ كَثِيرِ بْنِ دِينَارٍ، قَالَ حَدَّثَنَا بَقِيَّةُ، قَالَ حَدَّثَنَا شُعْبَةُ، قَالَ وَحَدَّثَنِي ابْنُ عَوْنٍ، وَخَالِدٌ الْحَذَّاءُ، عَنِ ابْنِ سِيرِينَ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم سَجَدَ فِي وَهْمِهِ بَعْدَ التَّسْلِيمِ .
It was narrated from Abu Hurairah that :The Prophet (ﷺ) prostrated after the salam when he was not sure
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih Isnaad
Al-AlbaniSahih Isnaad
Zubair Ali ZaiSahih
In-book reference: 13:57