The Two are One

Another example of the Old Covenant being united with the New Covenant is how we enter into both.  Under the Old Covenant a person was first born into the covenant of Abraham and then marked under the covenant by the act of circumcision.  For Christians we too come into the covenant first by birth (must be born again) and then by being marked which is our baptism, which is a circumcision of the heart (Col. 2).