Circumcision
The Book of Genesis contains only three of the 613 Mitzvot of the Torah. The commandment to marry and have children comes from the words, “Be fruitful and multiply.”
Avraham Avinu was the first to perform Brit Mila, and Yakov Avinu was told that Jews were not permitted to eat from the גיד הנשה, sciatic vein.
The concept of circumcision was to make a Jewish man complete. The removal of the foreskin symbolized the removal of the spiritual barrier that may separate the heart of man from his G-d. This was the opinion of the Keli Yakar.
The confrontation between David and Goliath reflected this idea. David was not intimidated by the giant. He referred to him as the ערל, uncircumcised one. He asked, “Who is this uncircumcised Phillistine, that he disgraces the battalions of the living G-d?” It seemed as though he had a clear advantage because of his Brit Mila.
The Sefer Hachinuch gives a beautiful rationale for the Mitzva of circumcision. He writes that just as the Jew is spiritually different from the Gentile, Hashem desired that he be physically different. Why was the sex organ chosen as the place where this sign of differentiation should be set? Because it is the organ of procreation. This implies that the uniqueness of the Jew should be apparent in every new generation that is born. Also, an uncircumcised male is considered imperfect. Circumcision brings man’s body closer to perfection.
Avraham received this commandment so that there would be no obstacles in his own personal quest for spiritual perfection. Rav Kook added that the foreskin was an impediment towards being able to absorb all of the holiness that existed in the land of Israel.