Sahih al-Bukhari 154
صحيح البخاري#154SahihNarrated Abu Qatada:The Prophet (ﷺ) said, "Whenever anyone of you makes water he should not hold his penis or clean his private parts with his right hand. (And while drinking) one should not breathe in the drinking utensil
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: 4:20