Why did Paul have to stand up against Jewish people from Jerusalem?
Paul had to stand against Jewish people from Jerusalem because they considered him a false teacher and an imposter. Alongside his physical sufferings, he continually defended his apostleship, and the love of Christ drove him to keep pressing on despite that opposition.
Les explains that Paul suffered inexorably for the sake of the Gospel and, along with all his physical sufferings, had to constantly defend his Apostleship. He had to stand up against the Jewish people from Jerusalem, who thought he was a false teacher and an imposter. In spite of all that opposition, only one thing kept driving him on: the love of Christ. Les also notes Paul’s background as a religious zealot under Judaism and as a Pharisee; God transformed and saved him by grace, but that personality kept going, and his energy was redirected out of love for Christ rather than to defeat His name.