The concepts in the New Testament were not derived out of thin air. Amos 3:7says, "Surely the Lord God does nothing unless He reveals His secret counsel to His servants the prophets." What is mentioned in the New Testament is revealed in the Old Testament either clearly or in types and figures. Genesis 22 is a great example of the sacrifice of Jesus, the Son inTypologyrepresented by the sacrifice of Isaac.
Some critics of Christianity state that Christianity borrowed its concepts from pagan sources like Mitrha, Osiris, Apollonius, etc. Admittedly, there are similarities in some pagan religions with Christianity, but that does not mean Christian writers borrowed from them any more than similarities between Communism and Democracy mean one is from another. Similarities abound in many religions. Hinduism has moral statements similar to Christianity, as does Taoism. But they are unrelated to each other.
There are, however, several reasons working against the idea that the people who wrote the New Testament copied ideas from pagan myths. First of all, the writers of the New Testament were Jews. As Jews they would have nothing to do with paganism in any form. They knew specifically that Jesus fulfilled the Old Testament which is why they followed Him. Second, the Old Testament has almost all the New Testament themes from which a devout Jew would refer when writing the New Testament. Third, there is no proof at all that the New Testament writers borrowed from pagan sources and incorporated them into the New Testament. It is up to the critics to supply reasonable evidence for this if they want to hold the position. Just saying it happened doesn't mean anything. Fourth, so what if there are similarities? What does it prove? If two writers in the same city both write similar articles about the President of the U.S., does it mean one used another's concepts? Not at all. Similarities happen all the time when dealing with similar subjects. Besides, it makes sense that common themes would be around an area at the same time in history when all nations served various gods. Undoubtedly, some similarities will occur, but that doesn't mean one was borrowed from another. Finally, there is another possibility worth examining. The concepts of redemption, the incarnation, resurrection, etc., are prophesied in the Old Testament and these documents were around for hundreds and hundreds of years. It is quite possible that if any borrowing was done, it was done by the pagans who incorporated Old Testament concepts since these documents existed prior to many of these pagan myths.
Nevertheless, following is a chart that exemplifies many of the themes that were revealed in the Old Testament and fulfilled in the New. It is easy to see that there is no need at all for the Christians to borrow from any source outside the Old Testament.
John 5:39, "You search the Scriptures, because you think that in them you have eternal life; and it is these that bear witness of Me."