Sahih al-Bukhari 290
صحيح البخاري#290SahihNarrated `Abdullah bin `Umar:`Umar bin Al-Khattab told Allah's Messenger (ﷺ), "I became Junub at night." Allah's Messenger (ﷺ) replied, "Perform ablution after washing your private parts and then sleep
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: 5:42