Sahih Muslim 1402 b
Sa'id b. al-Musayyib reported:
I heard Sa'd (b. Abi Waqqas) saying that the idea of 'Uthman b. Maz'un for living in celibacy was rejected (by the Holy Prophet), and if he had been given permission they would have got themselves castrated.
وَحَدَّثَنِي أَبُو عِمْرَانَ، مُحَمَّدُ بْنُ جَعْفَرِ بْنِ زِيَادٍ حَدَّثَنَا إِبْرَاهِيمُ بْنُ سَعْدٍ، عَنِ ابْنِ، شِهَابٍ الزُّهْرِيِّ عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، قَالَ سَمِعْتُ سَعْدًا، يَقُولُ رُدَّ عَلَى عُثْمَانَ بْنِ مَظْعُونٍ التَّبَتُّلُ وَلَوْ أُذِنَ لَهُ لاَخْتَصَيْنَا ‏.‏