Answer:
   
   The rite of circumcision is one of the most ancient practices of
   Judaism. The commandment to circumcise male children was given to
   Abraham in the Torah (Genesis 17:7-14) [English translation from 1917
   JPS Tanach]:
   
     And G-d said unto Abraham: 'And as for thee, thou shalt keep My
     covenant, thou, and thy seed after thee throughout their
     generations. This is My covenant, which ye shall keep, between Me
     and you and thy seed after thee: every male among you shall be
     circumcised. And ye shall be circumcised in the flesh of your
     foreskin; and it shall be a token of a covenant betwixt Me and you.
     And he that is eight days old shall be circumcised among you, every
     male throughout your generations, he that is born in the house, or
     bought with money of any foreigner, that is not of thy seed. He
     that is born in thy house, and he that is bought with thy money,
     must needs be circumcised; and My covenant shall be in your flesh
     for an everlasting covenant. And the uncircumcised male who is not
     circumcised in the flesh of his foreskin, that should shall be cut
     off from his people; he hath broken My covenant.
     
   It is repeated in the Torah in Leviticus 12:3, and has remained
   throughout history as one of the most important commandments. It has
   already led to martyrdom in Maccabean times (I Macc. 1:48,60).
   
   Circumcision is (in general) a common denominator among movements:
   Reform, Conservative, Reconstructionist, Orthodox--all circumcise
   their male children and require male converts to undergo some form of
   circumcision.
   
   Furthermore, faith is the only reason that Jews should circumcise
   their male children. In Moreh Nevuchim (Guide for the Pereplexed),
   chapter 49, the Rambam says: "No one, however, should circumcise
   himself or his son for any other reason than pure faith; for
   circumcision is not like an incision on the leg or a burn on the arm,
   but a very difficult operation."
   
   Current medical fashions play no role in circumcision, as it is a
   religous rite to Jews. Thus, it is pointless to attempt to argue for
   or against circumcision from a basis of medical need.
   
   As said in the Reform Responsa addressing circumcision: "Circumcision
   remains for us an essential sign of the covenant. We have affirmed it
   since the days of Abraham, our Father, and continue to affirm it".