But Zipporah took a flint knife and circumcised her son. She took the skin and touched his feet. Then she said to Moses, “You are a bridegroom of blood to me.”
In Christ you had a different kind of circumcision, one that was not done by human hands. That is, you were made free from the power of your sinful self. That is the kind of circumcision Christ does.
Abraham was circumcised later to show that God accepted him. His circumcision was proof that he was right with God through faith before he was circumcised. So Abraham is the father of all those who believe but are not circumcised. They believe and are accepted as people who are right with God.
A true Jew is one who is a Jew inside. True circumcision is done in the heart. It is done by the Spirit, not by the written law. And anyone who is circumcised in the heart by the Spirit gets praise from God, not from people.