Sahih al-Bukhari 157
صحيح البخاري#157Sahihحَدَّثَنَا مُحَمَّدُ بْنُ يُوسُفَ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ عَطَاءِ بْنِ يَسَارٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ تَوَضَّأَ النَّبِيُّ صلى الله عليه وسلم مَرَّةً مَرَّةً.
Narrated Ibn `Abbas:The Prophet (ﷺ) performed ablution by washing the body parts only once
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:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:23