Final answer:
The Epistle of Barnabas does not claim that both Jews and Christians will be saved; this is a misconception. Early Christian discussion, shaped by St. Paul, promoted the idea that Christ's salvation was for all, not limited to ethnicity or pre-existing religious affiliation.
Step-by-step explanation:
The claim that the Epistle of Barnabas suggests both Jews and Christians will ultimately be saved is false. The Epistle, instead, reflects early Christian views on the role of Judaism in God's plan after Jesus' arrival. Early Christian thought, influenced heavily by St. Paul, held that the salvation offered by Christ was universal, extending the potential for salvation beyond the Jewish community.
This was based on the belief that Jesus Christ fulfilled the prophecies of the Hebrew Bible, or the Old Testament, and was the Messiah foretold. While Christians, Jews, and Muslims share many foundational religious stories, their beliefs about the Messiah and salvation diverge significantly. Christians believe that Jesus Christ is the Son of God and that he has already appeared, offering salvation to all who believe, irrespective of their ethnic origin.
The first Christians were initially Jews, but as the teachings of Jesus spread, non-Jews or 'pagans' began to convert, leading to the belief in a potentially universal church. It should also be noted that while the Epistle is an early Christian text, it is not considered canonical by the majority of Christian denominations, and its views are not representative of mainstream Christianity.