It is narrated from Sayyiduna Samurah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever kills his slave, we will kill him; whoever cuts off a limb of his, we will cut off his limb; and whoever castrates him, we will castrate him."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6785