A non-Jewish slave belonging to a Jew is a slave for life unless the master puts out the slave’s eye or tooth, for the Torah has ruled: “If a man strikes the eye of his male or female servant, and destroys it, he shall let him go free for the sake of his eye. And if he knocks out the tooth of his male or female servant, he shall let him go free for the sake of his tooth” (Exodus 21:26-27). The sages ruled that it is not only the eye and the tooth which lead to freedom, but any exposed limb, like the eye or tooth, would lead to freedom for the slave if the master destroys it.
There was an incident in which the elders of the city did not come to hear the speech of the sage Rav Hisda. Rav Hisda, who was very zealous about the Torah’s honor, asked his student, Hamnuna, to go to the elders who were absent from the lesson and excommunicate them. Rav Hamnuna went to the elders of the city and asked them “Why did you not come to Rav Hisda’s lecture?” They answered: “Why should we go if when we ask him a question he cannot answer it?” Rav Hamnuna asked them “Have you then asked him a question which he could not answer?” The elders of the city asked him this question: If a master castrates his slave, does the slave go free? What are the issues under debate? Are the testicles considered exposed limbs like the tooth or eye, for which the slave goes free, or are they considered hidden limbs for which the slave does not go free? On one hand the testicles are exposed, yet on the other they are hidden within the scrotum. Rav Hamnuna did not have an answer for them. The city elders told him: You should not have been called Hamnuna, but Karnuna, one who sits at the street corners instead of being a scholar. Rav Hamnuna went to his teacher, Rav Hisda, and asked him the city elders’ question: are the testicles considered exposed limbs or hidden? Rav Hisda answered him that this question is based on a disagreement between early sages — according to one sage if the master castrated the slave by cutting off the sexual organ, which is considered an exposed organ, the slave goes free. According to another sage, Rabbi Judah the Nasi, the testicles are also considered exposed organs for which the slave goes free. A different early sage, Ben Uzzai, added that the tongue is also considered an exposed wound for which the slave goes free. The scholars asked: If so, because Ben Uzzai added the tongue, this means that according to Rabbi Judah the Nasi the tongue is considered a hidden limb, yet he explicitly stated that the tongue is considered an exposed limb. Answer: Rabbi Judah the Nasi also ruled the tongue to be an exposed limb for which the slave goes free; Ben Uzzai considers the testicles to be hidden limbs and the tongue to be an exposed limb.
(Babylonian Talmud, Tractate Kiddushin 24a-25b)