Hazrat Mutarrif (may Allah have mercy on him) narrates from a man that Hazrat Ibn Abbas (may Allah be pleased with them both) said: To castrate animals is mutilation. And then he (may Allah be pleased with him) recited this verse: { وَلآمُرَنَّہُمْ فَلَیُغَیِّرُنَّ خَلْقَ اللہِ }