How do we know that the B'ris Milah must be performed on the male organ?
Rashi and Ramban #1: From the words "Areil Zachar," which imply the part of the body that distinguishes between a male and a female. 1
Ramban #2 (citing Ibn Ezra): "Orlaso" (without specifying which) always refers to the location of the Ervah. 2
Ramban #3: The words "B'sar Orlaschem" (17:11) imply that one cuts off the flesh that covers a limb, and the only location on the body that fits that description is the flesh that covers the "crown" (of the male organ).
Seforno: The word "bi'Vesarchem" (in the previous Pasuk 17:13) is a refined word for the male organ. 3
Why does the Torah designate specifically the male organ for the Mitzvah of Bris Milah?
Seforno (to 17:13): Because it is the limb that is responsible for eternity, which B'ris denotes, and because it is the limb that creates the children, whom the B'ris includes. 1
When the Pasuk sentences someone who fails to perform the Bris Milah to Kareis, to whom is it referring?
Or Beis-Din, who are obligated to perform the Mitzvah where there is no father
What is the definition of Kareis?
Rashi: It means that the sinner will die childless, before his allotted time. 1
See Sifsei Chachamim.
QUESTIONS ON RASHI
Rashi writes: "'That soul will be cut off' (Kareis) - He will be "Ariri," and die before his time." What does "Ariri" mean, and how it is it implied in the Pasuk?
Gur Aryeh: "Ariri" means "childless;" either he will not father children, or his children will die young. 1 This is part of "Kareis," which means to be "cut off" at the source. One's children are comparable to the young branches of a tree; they too stem from the tree's roots.