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

Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).