The removal, by cutting, of the foreskin of the male penis. Though widely advocated in modern Western societies on the supposed ground of hygiene, circumcision is particularly associated with practising Jews by whom the rite is immensely valued as the occasion when a male child is initiated into the covenant of Abraham, eight days after birth (Lev. 12: 3).
However, as the OT itself (Jer. 9: 25–6) recognizes, circumcision was known amongst other peoples in the Near East, though not all required total amputation of the foreskin. The Hebrews had several versions of the origin of the rite—to Abraham (Gen. 17: 9–27), or to Moses (Lev. 12: 3) or to Joshua (Josh. 5: 2–7), and these served as useful justifications from Israel's traditions for the continuing insistence on the rite. In fact the origin may have been a kind of magic: a curious reference to this may survive in the story that Moses' wife saved his (Moses') life by circumcising their son (Exod. 4: 24–6).
At any rate circumcision was always a vital part of Jews' life—valued, exported (according to Josephus), defended even by martyrdom (1 Macc. 1: 48, 60) by the fervent, but detested by Jews who welcomed Hellenistic culture and desired assimilation to the Greeks. (Hellenized Jews took painful steps to cover up the embarrassment of circumcision by means of surgery.)
In the NT circumcision was an issue between Paul and the Jewish Christians who expected pagan converts first to become members of the covenant of Abraham by circumcision before being baptized as Christians. For Paul, this demand represented an attempt to add something to Christ, which was an absurdity: indeed it is virtually to reject Christ; it means that one has transferred one's allegiance to Christ alone on to an alternative system, namely the Law, in which circumcision is basic. The issue was whether the Church had taken over the role of the New Israel, or was a reformed Jewish sect.
There is no mention in the OT of the barbaric surgery of female circumcision traditionally practised in some African countries today and clandestinely in Britain but outlawed under Acts of 1985 and 2003.