text: If a Person is born Jewish but he is not circumcised , does that mean that he is not a member of the Abrahamic Covenant ?
  Thank you for your question.
  In the Old Testament, God commanded Abraham that he should circumcise himself, which is called Brit milah in Hebrew. The covenant was that Abraham and his descendants will circumcise themselves at 8 days old, and in turn God would give the children of Abraham the Promised Land, and that He will be their God. A Jew that is missing this is sorely lacking in his Jewish identity. In fact, circumcision, among other reasons, is specifically meant to be a symbol to show, “this person is a Jew and associates himself with Hashem, the God of the Jews”. Just to give you a few examples of how important circumcision is, the Midrash says, that Abraham himself stands at the door of gehinnom, and doesn’t allow any Jew that is circumcised in. Additionally, there are a number of commandments that carry a very strong punishment called Keret (spiritual severing from God and dying prematurely). Most of the commandments that carry this terrible consequence ae negative commandments, meaning that the person transgressed a serious offence, such as having sexual relations with certain relatives. There is only one such transgression nowadays of a positive commandment (a commandment of something that we must do) that carries such a punishment. That is not being circumcised.
  Having a circumcision performed nowadays is not quite what it was years ago. Nowadays the process itself is under anesthetic, and not painful. The next day you’ll be able to go to work. One other point, being Jewish depends on the person’s maternal lineage. If the person’s mother is not Jewish, the person would have to undergo conversion in order to be considered Jewish.