Circumcision was a “sign of the covenant” God made with Abraham (Gen. 17:11). The Lord had promised to make his descendants as numerous as the stars (15:5). Circumcision was a physical mark on that part of the male body most closely associated with fathering children (and therefore served as a continuing reminder of God’s fulfilled promise).
Male circumcision has known health benefits. God instructed Abraham and his descendants to circumcise baby boys on the eighth day of life. In the Expository Notes of Dr. Thomas Constable (at studylight.org), I found this fascinating quote: “At birth a baby has nutrients, antibodies, and other substances from his mother’s blood, including her blood-clotting factors, one of them being prothrombin. … After birth prothrombin decreases so that by the third day it is only 30% of normal. … On day eight [prothrombin] actually overshoots to 110% of normal, leveling off to 100% on day nine and remaining there for the rest of a person’s healthy life.” Today vitamin K is routinely administered to newborns just after delivery. Prothrombin depends on vitamin K for its production. But in the time before modern medicine, the eighth day was the best and safest for the male.
Many Christians practice male circumcision for health reasons, but it has no spiritual meaning. In the first century AD, some Jewish Christians tried to bind circumcision on the church, insisting that Gentiles undergo this procedure to be saved (Acts 15:1). But the inspired apostles rejected their argument. The disciples of Jesus are saved by Christ alone, apart from works of the law (Rom. 3:28).
Female circumcision (which is totally foreign to the Bible) has no health benefits whatsoever. If only a tiny piece of flesh is removed, no lasting harm is done (unless the cutting causes an infection). But female circumcision is painful and serves no purpose. God says that his commandments are for our “good” (Deut. 10:12-13).
Tragically, in many places female genital mutilation does a terrible disservice to women. They suffer real distress and the loss of the sexual pleasure God intended for them to experience in marriage. Muslim men are hurt by this abuse too. If a man’s wife isn’t enjoying intimacy with him, his own pleasure is diminished (even if he doesn’t know anything different).