Muwatta Malik · Hadith 1733
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 Umar disapproved of castration and said, "The completeness of the created form is in the testicles
Mauquf Sahih · Salim al-Hilali