What makes you a Jew is on the inside, a “circumcision of the heart” that doesn't follow the letter of the law but the Spirit. Someone like that is looking for praise from God, not from people.
It was actually before he became a Jew by being circumcised, which was a confirmation of his trust in God to make him right. This happened before he was circumcised, so he is the father of everyone who trusts in God and are considered as right by God, even though they may not be circumcised Jews.