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.
Mohel
Biblically, the infant's father ("avi haben") is commanded to perform the circumcision himself. However, as most fathers are not comfortable or do not have the training, they designate a "mohel". The mohel is specially trained in circumcision and the rituals surrounding the procedure. Many "mohalim" are doctors or rabbis (and some are both) or cantors and are required to receive appropriate training both from the religious and medical fields.