@NightTwister was right about circumcision being a sign of the Old Covenant. If it is a sign of salvation by grace through faith then every male ever born who believed should have been circumcised. Salvation has always been by grace through faith. How that salvation was/is to be worked changed through the age ie. by conscience, by the Law (Torah), by Spirit filled.
It's always been my understanding that circumcision was designed to teach, that in order for a person to enter a relationship with God, sin must be shed. The foreskin is a symbol of the sin nature hence, today circumcision is no longer required because Christ has dealt with the sin issue permanently.