I was at a Brit (circumcision) today, where the father spoke about how the Brit Milah is the entry point into the Jewish people. I'll admit that the father spoke well and showed some learning – However his fundamental point was wrong.
The Brit Milah is not a covenant between God and the Jewish people. It is a covenant between God and ALL the descendents of Abraham including those who are not Jewish. Some of you are probably staring at me right now, as has every person I've stated this to. Here is the Rambam's phrasing, found in Hilchot Melachim (chapter 10, Hilchot 7 and 8):
Halacha 7Only Abraham and his descendants were commanded regarding circumcision as Genesis 17:9-10 states: 'Keep My covenant, you and your offspring... circumcise every male.'The descendants of Ishmael are excluded as implied by Genesis 21:12: 'It is through Isaac, that your offspring will be called.' Esau's descendants are also excluded, for Isaac told Jacob Genesis 28:4: 'May God grant Abraham's blessing to you and your descendants,' implying that only he is the true offspring of Abraham who maintains his faith and his upright behavior. Thus, they alone are obligated in circumcision.
Halacha 8Our Sages related that the descendants of Keturah who are the offspring of Abraham that came after Isaac and Ishmael are also obligated in circumcision. Since, at present, the descendants of Ishmael have become intermingled with the descendants of Keturah, they are all obligated to be circumcised on the eighth day. However, they are not executed for failure to perform this mitzvah.
I'll add that you should not belittle a covenant between god and Abraham, even if it does not make you Jewish. There are other covenants with Abraham that are limited to the Jews, but not Brit Milah. Brit Milah is not the covenant of the Jews (That is actually Pesach) but rather the covenant where we accept God as our God.
Genesis 17, 7.
וַהֲקִמֹתִי אֶת-בְּרִיתִי בֵּינִי וּבֵינֶךָ, וּבֵין זַרְעֲךָ אַחֲרֶיךָ לְדֹרֹתָם--לִבְרִית עוֹלָם: לִהְיוֹת לְךָ לֵאלֹהִים, וּלְזַרְעֲךָ אַחֲרֶיךָ. 7 And I will establish My covenant between Me and thee and thy seed after thee throughout their generations for an everlasting covenant, to be a God unto thee and to thy seed after thee.
Other nations descended from Abraham have accepted god – but have not become Jewish. I'll leave it open to people to argue the theological implications of that statement.