Hadith 9:2
Ibn al-Mubarak narrated to us, from Ma'mar, from al-Zuhri, from Sa'id ibn al-Musayyib, from Sa'd, that the Messenger of Allah (may Allah bless him and grant him peace) rejected celibacy for Uthman ibn Maz'un. And had he permitted it for him, we would have castrated ourselves.
حدثنا بن المبارك عن معمر عن الزهري عن سعيد بن المسيب عن سعد أن رسول الله صلى الله عليه وسلم رد على عثمان بن مظعون التبتل ولو أذن له لأختصينا