Sahih al-Bukhari 5074
Sahih al-Bukhari · Book 67: Wedlock, Marriage (Nikaah) · What is disliked of not marrying and of getting castrated
Narrated Sa`d bin Abi Waqqas:
حَدَّثَنَا أَبُو الْيَمَانِ ، أَخْبَرَنَا شُعَيْبٌ ، عَنِ الزُّهْرِيِّ ، قَالَ أَخْبَرَنِي سَعِيدُ بْنُ الْمُسَيَّبِ ، أَنَّهُ سَمِعَ سَعْدَ بْنَ أَبِي وَقَّاصٍ ، يَقُولُ لَقَدْ رَدَّ ذَلِكَ ـ يَعْنِي النَّبِيَّ صلى الله عليه وسلم ـ عَلَى عُثْمَانَ، وَلَوْ أَجَازَ لَهُ التَّبَتُّلَ لاَخْتَصَيْنَا.
The Prophet (ﷺ) prevented `Uthman bin Mazun from that (not marrying), and had he allowed him, we would have got ourselves castrated.