Bris Mila
Rabbi Reuven Mann (Paraphrased by a student)
The question regarding circumcision is why this performance is the 'bris' - the treaty - made by God between Him and man.
Abraham was the one who God selected as the forefather of the new nation. There was nothing peculiar about Abraham over the rest of mankind, other than his attachment to a life based in reality, in discovering God, and his enjoyment and preoccupation in the study of reality.
Circumcision was the mark selected by God to render Abraham, and all man, perfected. What is this perfection of circumcision? I believe it is very basic: As the organ commanded in circumcision is one which affords man the ultimate in physical enjoyment, and as God desires that man immerse himself in the world of the metaphysical, i.e., knowledge, God therefore commanded circumcision to weaken man's attachment to the physical.
Maimonides says that man is created physically perfect. When man is circumcised, he enjoys that pleasure less, as does his partner. His reduction in physical enjoyment sets the stage for man's diminution in lusts, freeing up his energies to reattach to the real good in life - that being wisdom. Circumcision designates man for the true life.
Circumcision is an essential 'state', not only an action. We see this from the sons of Jacob. When in Sh'chem, the brothers referred to those uncircumcised people as "cherpah", disgraceful. That is, anyone who cleaves to the life of the physical desires by going uncircumcised is disgraceful in light of God's desire for mankind.
During the first Passover in Egypt, the Jews were commanded to perform circumcision. This perfection was required prior to the Exodus in order that the Jews in Egypt be saved by God. Without adherence to a life where Torah study and knowledge is supreme, and the physical is recognized only as a secondary means to Torah acquisition, man absorbs himself in physical lusts and desires, completely contrary to the philosophy outlined by the Torah. The Jews in Egypt would not merit salvation into a life of wisdom if they remained submerged in the Egyptian life of physical desires. Circumcision therefore was a requirement, timed precisely at the time of salvation, prior to receiving the gift of the Torah.