Sunan an-Nasa'i 54
سنن النسائي#54Sahihأَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا عَبِيدَةُ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ أَنَسٍ، قَالَ بَالَ أَعْرَابِيٌّ فِي الْمَسْجِدِ فَأَمَرَ النَّبِيُّ صلى الله عليه وسلم بِدَلْوٍ مِنْ مَاءٍ فَصُبَّ عَلَيْهِ .
It was narrated that Anas bin Malik said:"A Bedouin urinated in the Masjid, and the Prophet (ﷺ) ordered that a bucket (be brought) and poured over it
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
Al-AlbaniSahih
Zubair Ali ZaiSahih - Agreed Upon
In-book reference: 1:54