Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) said: "The Messenger of Allah (peace and blessings be upon him) forbade Sayyiduna Uthman bin Maz'un (may Allah be pleased with him) from tabattul, and had he (peace and blessings be upon him) permitted him tabattul, we would have castrated ourselves."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8283