As to why the Torah refers to circumcision sometimes as “brit”and other times as “ot brit,” the Abrabanel argues that explains that when one is in the midst of the act of circumcising, he is effecting the “brit,” but when that is completed, the everlasting result is the “ot brit” – the sign of the brit.
As far as the rationale of milah is concerned, the Abrabanel says milah brings a person to sh’leimut and saves him from descending to gehenna. As the Midrash states (Bereishit Rabbah 48:7), “R. Levi said: ‘In the time to come, Abraham will sit at the entrance of gehenna and not allow any of Israel who are circumcised to descend therein.’”
In answer to the last question, the Abrabanel notes: “Adam was not commanded to circumcise himself because Adam at his birth was not drawn to illicit passions and worldly desires; rather, he was drawn by his intelligence to understand that he was the creation of G-d’s own hands. Therefore the arla – the foreskin – was not a detriment to him. Accordingly, he was not commanded to circumcise himself. Indeed, that is what our sages (Avot D’R. Nattan 2:5) meant when they stated that ‘Adam was born circumcised’ [i.e., that he was complete and not in need of any further refinement]. However, once he ate of the etz ha’da’at – the tree of knowledge – he was drawn to worldly desires, and all the generations remained uncircumcised, as manifested by their uncontrolled desires. This remained until Abraham appeared and was commanded [to circumcise himself] for the sake of his becoming whole.”
The Abrabanel continues, “And I say that it was in order to rectify that which Adam perverted when he ate of the tree of knowledge and was expelled from the Garden of Eden [into the world] below that with the command [of milah] Abraham and all his progeny shall merit the Garden of Eden [in the world] above.”
When the phrase “progeny of Abraham” appears, the reference is to Isaac, as the verse (21:12) states: “ki b’Yitzchak yi’karei le’cha zara – since through Isaac will offspring be considered yours.”
(To be continued)