Kiddushin 24 - Tooth and eye
A type of slave designated as "Canaanite slave" is acquired with money and is the property of its owner. Nevertheless, if the master knocks out the slave's tooth or destroys his eye, whether by accident or on purpose, the slave acquires freedom. Moreover, if the master destroys "a tip of the slave's limb that does not regenerate," the slaves also goes free. There are twenty four such "tips": ten fingers, ten toes, two ears, the nose and the male member. But how do we know this? Only the eye and tooth are mentioned in the Torah!?
Well, easy: what is common between an eye and a tooth? The fact that they are exposed to view and they do not regenerate! - Therefore, we will include any other organ that is exposed to view and that does not regenerate, and these are the twenty-four mentioned above.
But we can suggest a counterargument: why do we need to mention a tooth after an eye was mentioned? Since the eye is in the open, and does not regenerate,
it already teaches the lesson, and I would know that a slave goes free when the master knocks out his tooth. If so, why was the tooth mentioned? - To limit freedom to only these two cases!
We can argue back: if only the tooth was mentioned, then I would include even the milk tooth. How do I know that a slave does not go free in this case? - By comparison with an eye, which does not regenerate.
Okay, but then the Torah should have mentioned just the eye! - No, for if it did, I would not include the tooth, since the tooth is not present at birth. Thus, both had to be mentioned, and the other twenty-four members are learned from them.
Art: Self-Portrait With Black Vase And Spread Fingers by Egon Schiele