Final answer:
Jews and Gentiles who believe in Jesus are considered 'one new humanity in Christ', reflecting the universalistic aspect of Christian salvation that is open to anyone, regardless of social or ethnic background.
Step-by-step explanation:
There is now no difference between Jews and Gentiles who believe in Jesus, because together they are now one new humanity in Christ. This concept arises from the belief that the salvation offered by Christ is universal, open to anyone who accepts Christianity's teachings, regardless of their ethnic or social background. The emphasis on spiritual equality and universal access to salvation, as found in the teachings of Jesus and the writings of St. Paul, has been a fundamental aspect throughout the history of Christianity. Despite the diverse beliefs among early Christians, they shared common themes like the potential openness of Christianity to all people and the recognition that no social distinctions should preclude individuals from belonging to the faith.