Muwatta Malik 1733

Arabic

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

Translation

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

Authenticity

Sahih · Salim al-Hilali

Reference