Sahih Muslim 1404cBook 16, Hadith 15
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ إِسْمَاعِيلَ، بِهَذَا الإِسْنَادِ قَالَ كُنَّا وَنَحْنُ شَبَابٌ فَقُلْنَا يَا رَسُولَ اللَّهِ أَلاَ نَسْتَخْصِي وَلَمْ يَقُلْ نَغْزُو .
" We were young, so we said: Allah's Messenger, should we not have ourselves castrated? But he (the narrator) did not say; We were on an expedition."