Circumcision symbolically represents a sacrifice of one's own self-will or pleasure, based on the notion that service of God, like all service of friends, families or communities, demands a degree of self-sacrifice.

Deut. 10:16. Circumcise therefore the foreskin of your heart, and be no longer stubborn

Jer. 4:4. "Circumcise yourselves to the LORD And remove the foreskins of your heart, Men of Judah and inhabitants of Jerusalem, Or else My wrath will go forth like fire And burn with none to quench it, Because of the evil of your deeds."

The physical act is a Besetzung/cathexis or placebo of the mental act.

Christians are relieved of this symbolism just as we are allowed to eat non-kosher animals. Our rapport with sacrifice is via our sympathy with the Eucharist.