Sahih al-Bukhari 158
صحيح البخاري#158SahihNarrated `Abdullah bin Zaid:The Prophet (ﷺ) performed ablution by washing the body parts twice
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:24