Sahih al-Bukhari 5074
صحيح البخاري#5074SahihNarrated Sa`d bin Abi Waqqas:The Prophet (ﷺ) prevented `Uthman bin Mazun from that (not marrying), and had he allowed him, we would have got ourselves castrated
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: 67:12