Sunan an-Nasa'i 22
سنن النسائي#22Sahihأَخْبَرَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا غُنْدَرٌ، قَالَ أَنْبَأَنَا مَعْمَرٌ، قَالَ أَنْبَأَنَا ابْنُ شِهَابٍ، عَنْ عَطَاءِ بْنِ يَزِيدَ، عَنْ أَبِي أَيُّوبَ الأَنْصَارِيِّ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا أَتَى أَحَدُكُمُ الْغَائِطَ فَلاَ يَسْتَقْبِلِ الْقِبْلَةَ وَلَكِنْ لِيُشَرِّقْ أَوْ لِيُغَرِّبْ " .
It was narrated that Abu Ayyub Al-Ansari said:"The Messenger of Allah (ﷺ) said: 'When any one of you goes to defecate, let him not face toward the Qiblah, rather let him face towards the east or the west
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:
In-book reference: 1:22