Christians should not circumcise. The external rite of circumcision mandated by the Law of Moses is to be replaced by the internal circumcision of the heart.
Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing.
(Gal:5:2)
In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ
(Col:2:11)