'Circumcision' in the Bible

And he gave to him the covenant of circumcision; and thus he begat Isaac and circumcised him the eighth day; and Isaac Jacob, and Jacob the twelve patriarchs.

And the faithful of the circumcision were astonished, as many as came with Peter, that upon the nations also the gift of the Holy Spirit was poured out:

and when Peter went up to Jerusalem, they of the circumcision contended with him,