Sunan an-Nasa'i 426
سنن النسائي#426Sahihأَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ شُعْبَةَ، عَنْ مُخَوَّلٍ، عَنْ أَبِي جَعْفَرٍ، عَنْ جَابِرٍ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا اغْتَسَلَ أَفْرَغَ عَلَى رَأْسِهِ ثَلاَثًا .
It was narrated that Jabir said:"When the Messenger of Allah (ﷺ) performed Ghusl, he would pour water on his head three times
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: 4:31