We ourselves are Jews by birth and not Gentile sinners; yet we know that a person is not justified by works of the law but through faith in Jesus Christ, so we also have believed in Christ Jesus, in order to be justified by faith in Christ and not by works of the law, because by works of the law no one will be justified.
Paul starts out by referencing his birthright, that of a Jew, one of God's chosen race. The Jews sinned as did the Gentiles, they just did it under a measure of grace, as God's chosen children. I believe that Paul wants all to understand that it was grace, and not their ability to live a sinless live that set the Jews apart. I believe this because he goes on to say that he knows that "a person is not justified by works of the law."
This is such a radical departure from his previous beliefs, but I believe that Paul now holds to this for 2 very important reasons. First, because God has opened his eyes to a very inconvenient truth (apologies to Mr. Gore). Without God removing the blinders, how can a man every honestly surrender his sincerely held misconceptions, especially when to change your thoughts comes at such a high cost? Second, having had his blinders removed, he could see the senselessness of what he had held to and the beauty of the truth. Can a man really live a sinless life and have the Almighty God of the universe look upon him with approval? Can a man hope to achieve salvation by following a set of rules? Is this the message of the Old Testament, the foundation for the gospel message? Or, was the Old Testament preparing us for the reality of Christ, and that by faith in him we might be justified?
This is the message of the gospel, and it is found somewhat hidden for some in the cracks of every passage. But I see it hiding in there, and I pray that you might see it to. Your rules, they do not save you. Try as you might to please God, you can't unless you first come to him in faith. You can't, unless you first see him as beautiful and love him. (Luke 19:20-27 comes to mind)
We are children of God by birth, and not Gentile sinners! Praise God!