Sunan an-Nasa'i 50
سنن النسائي#50Hasanأَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ الْمُخَرِّمِيُّ، قَالَ حَدَّثَنَا وَكِيعٌ، عَنْ شَرِيكٍ، عَنْ إِبْرَاهِيمَ بْنِ جَرِيرٍ، عَنْ أَبِي زُرْعَةَ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم تَوَضَّأَ فَلَمَّا اسْتَنْجَى دَلَكَ يَدَهُ بِالأَرْضِ .
It was narrated from Abu Hurairah that the Prophet (ﷺ) performed Wudu', and when he had performed Istinja' he rubbed his hand on the ground
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 GhuddahHasan
Al-AlbaniHasan
Zubair Ali ZaiIsnaad Hasan
In-book reference: 1:50