Musnad Ahmad 8:87

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, who said: Sa'id ibn al-Musayyib informed me, from Sa'd ibn Abi Waqqas, who said: "The Messenger of Allah (may Allah bless him and grant him peace) rejected celibacy for Uthman. And had he permitted it for him, we would have castrated ourselves."