(3) باب نِكَاحِ الْمُتْعَةِ وَبَيَانِ أَنَّهُ أُبِيحَ ثُمَّ نُسِخَ ثُمَّ أُبِيحَ ثُمَّ نُسِخَ وَاسْتَقَرَّ تَحْرِيمُهُ إِلَى يَوْمِ الْقِيَامَةِ
This hadith has been narrated on the authority of Isma'il with the same chain of transmitters (and the words are):
" 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."
Reference: Sahih Muslim 1404 c
In-book reference: Book 16, Hadith 15
USC-MSA web (English) reference(deprecated numbering scheme): Book 8, Hadith 3245