Siman 24

Male intercourse and intercourse with a beast are among the forbidden relations and carry the penalty of kareth; and if there were witnesses and a warning, one is liable for stoning, as is explicit in the Torah. Therefore, one who lies with a male or brings a male upon himself, once he has performed initial penetration, if both were adults—they are stoned. As it is said: "And with a male you shall not lie as one lies with a woman" (Leviticus 18:22), and in Kedoshim it is written: "And a man who lies with a male as one lies with a woman, both of them have committed an abomination; they shall surely be put to death, their blood is upon them" (Leviticus 20:13). Behold, the one who lies and the one who is lain with are both subject to stoning, and the negative commandment of "you shall not lie" also applies to both of them—read it as "lo tishkav" (you shall not lie) and "lo tishakev" (you shall not be lain with) [Sanhedrin 54b], for the Scripture does not punish unless it first warns with a negative commandment. And if one of them was a minor—if he is nine years and one day old, the adult is liable for stoning and the minor is exempt; and if he is less than this—even the adult is exempt, and the beit din shall strike the adult with lashes of rebellion.

The Rambam, of blessed memory, wrote in chapter 1 of Issurei Biah, law 15: One who comes upon an androgynos by way of his male organ is liable, and the tumtum is a doubt; therefore, one who comes upon a tumtum, or upon an androgynos by way of his female organ, is lashed with makat mardut, and the androgynos is permitted to marry a woman. Thus far his words. It is clear from his words that an androgynos is judged as a male, and even though for the entire Torah he is a doubt whether male or female, as the Rambam himself wrote regarding the impurity of childbirth in chapter 10 of Issurei Biah, and regarding arachin in chapter 1 of Arachin, and regarding the seeing of blood in chapter 1 of Mishkav U-Moshav, and likewise in chapter 2 of Ishut and Nezirut, see there; nevertheless, here the Torah included him from the inclusion of "And with a male you shall not lie the lyings of a woman," that from the place of his male organ, when he is lain with, he is judged as a male, and automatically since this is so, there is no prohibition in his taking a wife. [And regarding what is challenged against Resh Lakish in Yevamot 82a from marrying, see Noda Bi-Yehudah Tinyana section 1, and see Rambam chapter 7 of Terumot and in Kesef Mishneh there]. And it is a simple matter that according to the Rambam, also an androgynos who comes upon a male is liable to the death penalty, and perhaps he is liable for all arayot, or it is possible that the Torah only included him regarding mishkav zachar [see there 83a], but there are those who disagree with him and hold that ultimately an androgynos is a doubt and one is not liable for him at all, and also he is not liable for anything and does not marry a woman [so it appears from Rashi there 83a who explains that the halacha is like Rabbi Yose of the Mishnah, and so it appears from the Rashba there, and see Kesef Mishneh and delve into it].

One who copulates with a domestic animal or with a wild animal or a bird, or who brings them upon himself—both are stoned, as is explicit in the Torah. For even though the animal did not sin, nevertheless, since a great stumbling block came to a person through it, the animal is also killed, as it is written: "and you shall kill the woman and the animal" (Leviticus 20:16). And there is no distinction between a man who copulates with an animal or brings it upon himself, or a woman who is copulated with by an animal or brings the male upon her. And there is no distinction between a large animal and a small one, as it is written (Leviticus 18:23): "And with any animal"—even one day old, for an ox of one day is called an ox. And that which is written "animal"—the same applies to a wild animal and a bird, and throughout the entire Torah it is so, such as regarding the labors of Shabbat. And also regarding an animal, there is no distinction between natural and unnatural intercourse, just as with a woman, for once he has achieved initial penetration with the animal or the animal has achieved initial penetration with him—he is liable.

One who lies with a beast unintentionally, and a woman who brought a beast upon herself unintentionally, where the person is exempt—the beast is also not put to death. For even though it is a disgrace for the person when the beast walks about and they say, "This is the beast that so-and-so came upon," nevertheless, our sages of blessed memory were in doubt [Sanhedrin 55b] whether that which the Torah commanded to kill the beast is specifically when there is also a stumbling block, meaning intentionally. And since it is a doubt—a doubt regarding the life of a beast is ruled leniently. Nevertheless, it is disqualified from the altar in all cases. And it appears to me that it is forbidden even to a commoner, for a doubt regarding a prohibition is ruled stringently and it is a doubt of Torah law. And similarly, regarding a star-worshiper who comes upon a beast, the beast is not stoned, as the Rambam wrote in the ninth chapter of Kings. And even though he is forbidden in this, for this is of the seven Noahide laws and there is a stumbling block, nevertheless, our sages of blessed memory were in doubt whether the primary reason is on account of disgrace, and by them there is no disgrace. And even though according to the sugya of the Shas it is explained there that in one of them the beast is killed regardless, see there, nevertheless, since ultimately for us there is a doubt in both of them, therefore the Rambam ruled in both of them leniently. And nevertheless, it is certain that if upon one beast an Israelite came unintentionally and a star-worshiper intentionally—that regardless it is killed. And know that for a commoner it is not forbidden except by two witnesses and not by one witness and not by the owners, and similarly it is not stoned through them except by two witnesses [Temurah 28a], and only for the altar is it forbidden in any case [ibid.]. And one should not ask why it is not stoned by one witness or by the owners when he came upon it intentionally, for there is a stumbling block and disgrace, for this has no connection to that; for just as a person is not killed without two witnesses, so too a beast, for as the death of the owners so is the death of the ox [it appears to me].

And even though in a case of an unintentional act the animal is not stoned as has been written, nevertheless, a minor when he is nine years and one day old who has relations with an animal, or a female minor older than three years who brought an animal upon her, even though they are not liable for death and their status is like those who act unintentionally—nevertheless the animal is stoned because of them, for there is a stumbling block and disgrace, since they are not acting unintentionally but are completely intentional, except that the Torah had pity on minors because their intellect is not yet complete, and therefore the animal is killed [Sanhedrin ibid.]. But when the male minor was less than nine years and one day, and the female minor was less than three years and one day—the animal is not stoned because of them since they are not fit for relations [ibid.].

Even though yichud is forbidden with all those subject to the laws of forbidden relations, nevertheless, regarding a male and an animal, there is no prohibition to be in seclusion with them, as Israel is not suspected of this—regarding male intercourse or regarding an animal. However, if one distances himself even from yichud with a male or an animal, he is praiseworthy, and the greatest of the sages would distance the animal so that they would not be in seclusion with it. In places where the licentious have increased in this regard, one must be careful and distance himself from yichud with them. In our countries, this is only a measure of piety [Bach]. Nevertheless, one should prevent two bachelors from sleeping together in any location; however, we do not practice this, and Heaven forbid, we have never heard to be concerned for this, and one who is careful, may a blessing come upon him.

And know that regarding domestic animals and wild animals, the laws of a male copulating with a human and a human copulating with a male animal apply, but regarding birds there is only a human copulating with a male bird, and a male bird copulating with a human does not exist [Rashi Chullin 23a]. And regarding fish, it appears that copulation with a human is not applicable at all, and furthermore, only land species are included in the general category of domestic animals [Tosafot Bava Kamma 55a s.v. atya, and see there in Tosafot s.v. hamanehig and v'yesh lomar ki heichi etc., and it requires further study for the practical law].