Circumcision
Circumcision is very important to most branches of Judaism, with over 90% of male adherents having the procedure performed as a religious obligation. The basis for its observance is found in the Torah of the Hebrew Bible, in Genesis chapter 17, in which a covenant of circumcision is made with Abraham and his descendants. Jewish circumcision is part of the "brit milah" ritual, to be performed by a specialist ritual circumciser, a "mohel", on the eighth day of a newborn son's life, with certain exceptions for poor health. Jewish law requires that the circumcision leaves the glans bare when the penis is flaccid. Converts to Conservative and Orthodox Judaism must also be circumcised; those who are already circumcised undergo a symbolic circumcision ritual. Circumcision is not required by Judaism for one to be considered Jewish, but some adherents foresee serious negative spiritual consequences if it is neglected.
Religious male circumcision
On the other hand, the emperor Hadrian (117-138) forbade circumcision. His successor Antoninus Pius (138-161) upheld the decree, but around 140 included an exemption for Jews who circumcised their sons, although not their servants, slaves, or converts. Even before that, in 95 CE, Flavius Clemens, a nephew of the emperors Titus and Domitian, suffered the penalty of death for undergoing circumcision, and embracing the Jewish faith with his wife Domitilla (see Grätz, "Gesch." iv. 403 et seq., 702).