Why is circumcision restricted to males in the Old Testament?

The simple answer is that the Torah gives a biological reason, not a theological one. Genesis 17:11 says the sign is cut "in the flesh of your foreskin" (besar 'orlah, בְּשַׂר עָרְלָה). Only males have the body part the sign requires. The text offers no creation-order argument — it does not say males are spiritually superior or that they represent their households before God in a unique way. It simply says: this sign is cut into this specific part of the male body. The restriction is anatomical.

הִמּוֹל לָכֶם כָּל זָכָר

"Every male among you shall be circumcised." — Genesis 17:10

What makes this clearer is comparing the covenant-sign vocabulary across the Torah. The same cluster of terms — 'ot (H0226, sign), berit (H1285, covenant), bein (H0996, between), dor (H1755, generations) — defines both circumcision in Genesis 17 and the Sabbath sign in Exodus 31. Both passages use the same form, the same language, the same theological structure. But Genesis 17 restricts the physical sign to males (zakar, H2145, vv. 10, 12, 14), while Exodus 31 applies its sign to all Israel — men and women — without gender restriction. The covenant-sign form itself is not gendered. Only the biological enactment of this particular sign requires a male body.

The Torah begins pointing beyond the physical sign almost immediately. Deuteronomy 10:16 commands: "Circumcise the foreskin of your heart" (umaltam 'et 'orlat levavchem, H4135 Qal imperative) — addressed to the whole congregation. Deuteronomy 30:6 goes further: YHWH himself will circumcise hearts. Jeremiah 4:4 repeats the same command. The sign was always pointing toward something the physical act could not achieve.

Paul draws the line to its end in Romans 2:28–29 — "circumcision is of the heart, by the Spirit" — and in Romans 4:9–11, where he observes that Abraham was counted righteous before circumcision. The sign was a seal of an existing righteousness, not its cause. Colossians 2:11–12 applies "the circumcision of Christ" to all believers without gender restriction. Paul does not attack the Torah's male restriction — he shows what the sign was always pointing to, and in that telos, the physical restriction becomes irrelevant.

For the full vocabulary-echo table comparing Genesis 17 and Exodus 31, see Men and Women Under Torah, section "Commands Directed to Men."