As Paul traveled around the Roman world, he had made numerous disciples in various places. They were all regular people, and they all had different home towns. But they began to congregate around him, and the truly international nature of the Christian church began to take shape. It was becoming visible. The secularists play at unity and diversity, but it always veers to one side or the other. It either collapses into an anarchic mess, or it solidifies into a total state.
Only Christ can give us form and freedom together. Paul had gathered these men together, and he was going to Jerusalem with them, a trip that would certainly underscore the point.