وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّهُ كَانَ يَكْرَهُ الإِخْصَاءَ وَيَقُولُ فِيهِ تَمَامُ الْخَلْقِ ‏.‏

Yahya related to me from Malik from Nafi that Abdullah ibn Umardisapproved of castration and said, "The completeness of the createdform is in the testicles." Translation Not Available

Book Ref: Muwatta Imam Malik Book 51 Hadith 1736
Web Ref:  Muwatta Imam Malik Book 51 Hadith 4