Actually, I think it was found that medically, it was beneficial to circumcise a child. I don't know the history or logic of it, but I was told that many, many years ago. Otherwise, only those that are Jews and perhaps Muslim actually practice that, and I'm not sure about Muslims.
With regards to Christianity, after salvation was offered to Gentiles as well as Jews, there was some controversy in that some in Christianity thought that the Gentiles also needed to be circumcised, but the Apostles put an end to that. Gentiles did not have to be circumcised.
Terry,
I will try to briefly explain the basics for you. Physical circumcision was implemented by God under the older covenant (testament) for the Jewish people as a sign of the law which set them apart from the Gentile. It was only for the Jew, and never the Muslim as we call them today. Those Jews were living under the law of God handed down to them through Moses.
The Son of God (Jesus/Yeshua) came to fulfill the covenants of the older covenant (testament). The newer covenant allowed for the reconciliation of man back to God, first to the Jew and then to include the Gentile secondly. All Jewish males older than eight days were circumcised at that time. Of course, not all Jews accepted Jesus as their Messiah and they remain(ed) living under the old law. The Messianic Jews are those Jews living under the new law or new covenant.
When Gentiles began to accept Jesus thru the gospel, the Jews naturally assumed the new Gentile converts should be circumcised as a sign to set the apart from the other Gentiles. Paul taught that under the new law there was no need of a physical circumcision, but rather the need of a spiritual circumcision of the heart.
I hope that explains things a little better.
dave