If you can call yourself a Jew, and you really trust in the Law, and are proud of your God, and know his will, and tell right from wrong because you have been taught by the Law;  if you are confident that you are a guide to the blind and a beacon to those in the dark, that you can teach the ignorant and instruct the unlearned because the Law embodies all knowledge and all truth – so then, in teaching others, do you teach yourself as well? You preach that there is to be no stealing, but do you steal? You say that adultery is forbidden, but do you commit adultery? You detest the worship of objects, but do you desecrate holy things yourself? If, while you are boasting of the Law, you disobey it, then you are bringing God into contempt. As scripture says: It is your fault that the name of God is held in contempt among the nations.

Chapter 2:25-29 Circumcision will not save them

Circumcision has its value if you keep the Law; but if you go on breaking the Law, you are no more circumcised than the uncircumcised. And if an uncircumcised man keeps the commands of the Law, will not his uncircumcised state count as circumcision?  More, the man who, in his native uncircumcised state, keeps the Law, is a condemnation of you, who, by your concentration on the letter and on circumcision, actually break the Law. Being a Jew is not only having the outward appearance of a Jew, and circumcision is not only a visible physical operation. The real Jew is the one who is inwardly a Jew, and real circumcision is in the heart, a thing not of the letter but of the spirit. He may not be praised by any human being, but he will be praised by God.