Sahih al-Bukhari 239
صحيح البخاري#239SahihThe same narrator said that the Prophet (ﷺ) had said: "You should not pass urine in stagnant water which is not flowing then (you may need to) wash in it
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: 4:105