As Christianity grew in its first centuries, it became an increasingly non-Jewish – occasionally even anti-Jewish – religious movement. Yet as early Christians struggled to define themselves as separate from the Jews, they also began contemplating and discussing a peculiar sign: the circumcision of Jesus, whom they considered God’s Son made flesh. Why would they be so drawn to this paradigmatic sign of the Jewish covenant on the body of the Christian messiah? What did it signify to them about the nature of religious and cultural boundaries? Professor Andrew Jacobs discusses diverse sources from Christian antiquity, but looks especially at the writings of Epiphanius, a bishop who took it upon himself to refute one Christian “heresy” that dared to teach: “Christ was circumcised, we should be too!”