“Circumcision” was the ceremony of cutting off the foreskin of a male's penis. This was a common rite among many people in the ancient Near East, though the reasons why are not clear. It may be that the blood of a circumcision was thought to have protective power, as when Zipporah circumcised her son to protect Moses from death (Exod 4.24-26).

Circumcision is first mentioned in the Bible in connection with God's promise to make Abraham's descendants a great nation and to give them a land they could call their own. In return, Abraham and his descendants were to obey God. To show that they were keeping their promise to God, every male descendant of Abraham was to be circumcised (Gen 17.1-14). Even non-Israelite men who wanted to be part of the Israelite people were to be circumcised (Gen 34.21-24). Circumcision became a requirement of the Law of Moses (Lev 12.3). The New Testament reports that both John the Baptist and Jesus were circumcised eight days after being born (Luke 1.59; 2.21).

The prophet Jeremiah warned that the outward practice of circumcision alone was not a true sign of being one of God's people, since other nations also practiced circumcision. The important thing was to worship God. His strong words to the people of Judah were, “Your bodies are circumcised, but your hearts are unchanged” (Jer 9.25-26). Later, he described a final and permanent renewal of the agreement with God that would be written on the people’s “hearts and minds” (Jer 31.31-34). The writer of Hebrews in the New Testament used Jeremiah's words to back up his message that the first agreement based on God's Law has been replaced by a new agreement brought by Christ (Heb 8.1-13).

The practice of circumcision caused arguments and division among early Christians. Some Jewish Christians who had lived according to the Law of Moses felt that they and any Gentile (non-Jewish) follower of Christ should obey all the Jewish laws and practice all its rituals, including circumcision (Acts 11.1,2; 21.17-24). Others, especially the apostle Paul, challenged the belief that Gentiles had to be circumcised in order to be acceptable to God. Paul had been circumcised and was a strict follower of the Law of Moses (Phil 3.2-6). But he came to believe that Gentile men could be acceptable to God and become part of God's true people, even if they were not circumcised. Paul argued that being circumcised is worthwhile only if a person can obey the whole Law of Moses. If someone does not obey the whole Law, circumcision cannot make that person “a real Jew.” Like Jeremiah, he believed true circumcision is something that happens in the heart (Rom 2.25-29). People are acceptable to God, not by doing everything the Law requires, but because they have faith (Rom 3.28; Phil 3.7-9).

Paul also criticized people he called “troublemakers,” Jews who insisted that Gentile believers must practice the Jewish rites, such as circumcision (Gal 1.6-9; 6.12-14; Phil 3.2). Paul said it was wrong for them to argue that being circumcised was the way to “complete” what God's Spirit started (Gal 3.1-3). In the end, Paul said simply, “It doesn't matter if you are circumcised or not. All that matters is that you are a new person” (Gal 6.15).