The Covenant of Circumcision
Male converts to Judaism are traditionally required to undergo circumcision or, if already circumcised, a ritual removal of a single drop of blood.
Whereas the Orthodox and Conservative movements require circumcision or, for those already circumcised, the ritual extraction of a drop of blood for a conversion to be valid, the Reform movement gives more latitude to individual rabbis. The latest official Reform position is that rabbis should educate converts about these traditional rituals, but have the choice to either counsel the conversion candidate to undergo the ceremonies (this being the preferred option) or to allow the candidate to choose whether or not to do so. Reconstructionists have a similar position to the Reform movement. Excerpted with permission from Choosing a Jewish Life: A Handbook for People Converting to Judaism and for Their Family and Friends (Schocken Books).
Brit milah [circumcision] is sometimes referred to as the covenant of Abraham, who circumcised himself in order to become a Jew. According to the midrash [scriptural interpretation], the timing of Abraham's act had special significance.
"Abraham was 48 years old when he came to know his creator. Yet he was not commanded to circumcise himself at that time and waited until he was much older--99 years of age.
Why? In order not to close the door upon proselytes, however advanced in years."
Actually, there is no explicit commandment in the Torah requiring circumcision (or immersion) for proselytes. The Talmud--the Oral Law--is where the laws and debates about initiation rites are found. There was general, though by no means universal, agreement among the rabbis that male converts must undergo both circumcision and mikveh [immersion in a ritual bath]. (Women only have to immerse.)
Despite the pain and risk that attended adult circumcision prior to the invention of anesthetics and antiseptic practice, adult men in every generation have submitted to circumcision in order to become Jews. Today, Orthodox and Conservative Jews still require circumcision or hatafat dam brit [extracting a drop of blood], its ritual reenactment. The Reform movement has accepted converts without milah or mikveh since 1892, a decision based in part on the absence of biblical law and also upon minority positions in the Talmud that argued circumcision was not the sine qua non for conversion. While the Reform and Reconstructionist movements do not require milah or mikveh, an increasing number of rabbis affiliated with both do make it a condition for their conversion candidates, so check with your rabbi.
Given the historical and religious significance of brit milah, the idea that an uncircumcised man can be a Jew seems like a logical impossibility. However, the case has been made that, like the uncircumcised Russian Jews who embraced their birthright after immigrating to the United States or Israel, uncircumcised converts may be seen as Jews in need of circumcision--but Jews nonetheless.