What was the crowning reason Paul declared there is no difference between Jew and Gentile?
The crowning reason was the scriptural fact that there is none righteous, no not one. Since both Jew and Gentile are unrighteous—not even the most religious Jew is righteous—there is no difference between them. Paul declared this because all are equally unrighteous before God.
Les explains that Paul's statement sent the Jewish community into orbit because they had been taught for almost 2000 years that they were special—God's covenant people, set apart from the rest of the world, not to intermarry, and to stay within their tribes. They were infuriated that Paul was taking the salvation of Israel's God to pagan Gentiles, so they plagued him every step of his way, followed him from city to city, tried to defeat him, and plagued him until his death. But the crowning reason Paul put out the declaration that there is no difference between Jew and Gentile is the verse he cites: 'There is none righteous, no not one.' The Pharisees, who were righteous in their own eyes, could have put him to death for this, because he made it plain that no one is righteous—not even the most religious Jew.