Sahih Muslim 3406
صحيح مسلم#3406SahihSa'id b. al Musayyib heard Sa'd b. Abi Waqqas (Allah be pleased with him) saying that Uthman b. Maz'un decided to live in celibacy, but Allah's Messenger (ﷺ) forbade him to do so, and if he had permitted 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 Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 16:9