God really is dong a new thing among the early Church, and sometimes it’s hard to know where the old rules stop and the new covenant begins. This is a good example as the Jews claim that circumcision, the covenant given to Abraham, must be practiced among all of them. This is actually pretty reasonable. God made the covenant with Abraham, after all, and God set that rule up. But God is going beyond the action, he wants his Church to have the faith as well. So it is that circumcision came to an end, but the faith of Abraham is still what we participate in.