كتاب النكاح
16  
The Book of Marriage
(1)
Chapter: Marriage is recommended for the one who desires it and can afford it, and the one who cannot afford it should distract himself by fasting
(1)
باب اسْتِحْبَابِ النِّكَاحِ لِمَنْ تَاقَتْ نَفْسُهُ إِلَيْهِ وَوَجَدَ مُؤْنَةً وَاشْتِغَالِ مَنْ عَجَزَ عَنِ الْمُؤَنِ بِالصَّوْمِ
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 ‏.‏
Reference : Sahih Muslim 1402b
In-book reference : Book 16, Hadith 8
USC-MSA web (English) reference : Book 8, Hadith 3238
  (deprecated numbering scheme)