After introducing the prohibition against offering a blemished animal as a sacrifice, and listing the disqualifying blemishes, the Torah (Vayikra 22:24) commands, “U’be’arsechem Lo Ta’asu” – “You shall not do so in your land.” This is understood as referring specifically to the blemishes involving the male reproductive organs, such that the Torah here forbids causing such defects. This verse, then, introduces the prohibition against castrating male animals or humans.
The Sefer Ha’hinuch explains that the Torah forbids castration because G-d wants all creatures to reproduce and multiply. Indeed, we are commanded, “Peru U’rebu” – to procreate, and the animal species, too, are intended to multiply upon the earth. The Sefer Ha’hinuch writes that as all creatures are mortal, G-d wants the members of all species to reproduce so as to ensure their perpetuation, as each species was especially created by the Almighty, and must therefore be maintained. One who castrates a creature shows that he does not wish for that species to multiply, and thus expresses disdain for one of G-d’s creations, indicating that he wants this species to disappear and not propagate. The Sefer Ha’hinuch’s comments are very relevant to modern times, when people advocate for a lifestyle which does not allow for reproduction. The Torah teaches us that G-d wants all creatures – certainly including human beings – to procreate, and one of our most important obligations is to do what we can to create new life.
It is forbidden even to instruct a gentile to castrate an animal owned by a Jew. If, however, a gentile castrated a Jew’s animal without being asked to do so, the Jew may take the animal back and benefit from it. But if the Jew hints to the gentile that he wants his animal castrated, and the gentile castrated it, the Jew may not then use the animal. In such a case, the Rabbis impose a penalty on the Jew and forbid him from benefitting from the animal.
If a person severed one part of the animal’s reproductive organ, and another person severed the remaining part, they are both liable to Malkut for jointly transgressing this prohibition.
A man is not allowed to make himself sterile even indirectly, by drinking a potion which causes sterility. However, one is not liable for Malkut by making himself sterile in this fashion. Likewise, the Sefer Ha’hinuch writes that one may not place his fellow in the snow to make him sterile. If he does so, he receives Malkut Mi’de’rabbanan (by force of Rabbinic enactment).
Women are not bound by the obligation of Peru U’rebu. Therefore, when the need arises – such as if a woman has a medical condition which makes pregnancy or childbirth dangerous – she may cause herself to become sterile.
This prohibition applies in all places and all times, and to both men and women, as a woman is forbidden from castrating an animal or a male human being. One who violates this command is liable to Malkut.