The belief that assigned Christianity as a separate religion from Judaism is often connected to the understanding of Jesus Christ's identity and mission, particularly the belief in Jesus as the Messiah (or Christ) and the Son of God. This belief, along with the concepts of salvation through faith in Jesus and the teachings of the apostles, particularly Paul, played a significant role in distinguishing early Christians from Jews.
In particular, the Council of Jerusalem (circa AD 50) addressed the inclusion of Gentiles into the Christian faith without requiring them to fully adhere to Jewish law, further differentiating Christianity from Judaism. Additionally, the belief in the New Covenant established by Jesus, which was seen as fulfilling and thus superseding the Old Covenant of Judaism, contributed to the separation of the two faiths.
Over time, as the followers of Jesus began to form their own communities and practices that diverged from those of the Jewish faith, Christianity evolved as a distinct religious identity. The development of key theological concepts, liturgical practices, and church governance further solidified its status as a separate religion.