The eighth day following birth plays a critical role concerning both a human male and a sacrifice. It also is the day that the Kohanim were inducted into service at the Sanctuary. [Aharon and his sons were instructed to wait in the Ohel Moed for seven full days while Moshe Rabbeinu performed the inauguration service. The inauguration service concluded with the induction of Aharon and his sons as Kohanim on the eighth day.] What is so special about the eighth day? Horav Moshe Feinstein, zl, cites the Midrash (Vayikra Rabbah 27:10) which states that both an animal and a human must live through a Shabbos before achieving offering/circumcision status. Apparently, Shabbos plays a pivotal role in the preparation of both the child and the korban. Rav Moshe explains that mitzvah performance, if it is to have any value, must be predicated upon our belief in Hashem. Indeed, if one who does not believe in Hashem were to recite a berachah, blessing, we may not answer amen. Such a person believes that Hashem is merely a term, a word without significance. Furthermore, Rambam (Hilchos Yesodei Torah 6:8) writes that a Sefer Torah she’kasvah min, a Torah scroll written by an apostate, should be burned. It lacks intrinsic sanctity. The term min, apostate, applies not only to one who completely denies the existence of Hashem, but also applies to one who (like Aristotle) believes that Hashem is the Master of the world, but not its Creator.
Shabbos attests to Hashem as the Creator of the world. Thus, the requirement is that a sacrifice must experience a Shabbos prior to its being offered up to Hashem. This implies that a korban is acceptable only from one who realizes and acknowledges that the offering is not his per se, but actually belongs to Hashem, the Creator of the world. This idea applies to all korbanos. One must affirm his belief in Hashem as Creator.
Likewise, the kedushah, sanctification, of the Kohanim and the Mishkan is contingent upon the belief that everything belongs to Hashem, because He is the Creator. To support this, we see that Hashem commanded the Jews (V’yikchu Li terumah; “And take for Me a portion” Shemos 25:8) without specifying its purpose. If everything that one has belongs to Hashem, however, it is not necessary for Hashem to state the reason that He wants the contribution. After all, it has always been His money. The Mishkan can be built only if people realize that Hashem is the true owner of all one’s possessions. [We may suggest that this concept applies to any davar she’b’kedushah, holy endeavor. If it is to achieve success, the contributor should realize that, in this endeavor, he is paying back, channeling back that which belongs to Hashem. The problem begins when he thinks that his check licenses him to offer an opinion, exert control and make demands.]
The same concept of acknowledging Hashem as Creator applies with regard to Bris Milah, at which time the chinuch, Torah education, of a Jewish boy, commences. The message is clear and unequivocal: A child must be made aware of the fundamentals of Judaism, specifically that Hashem created the world ex-nihillo. Whatever exists is from Him. Whatever we succeed in creating/making is only with His “assistance.” [If such a term even applies, since Hashem does not assist, He does it all! He allows us to think that we are doing something.] Hence, Bris Milah is performed once a child has experienced a Shabbos, which attests to Hashem’s creation of the world.