Christians claim that Paul of Tarsus wrote most of the letters of the New Testament and that what he wrote came from God himself.  Actually whoever wrote these letters borrowed many of their ideas from the Greek philosopher Plato who lived about 400 years earlier.

Moreover, if those who are called philosophers, and especially the Platonists, have said aught that is true and in harmony with our faith, we are not only not to shrink from it, but to claim it for our own use from those who have unlawful possession of it.

Augustine of Hippo, 354-430 CE

Further reading

Price, Robert M., The Amazing Colossal Apostle

Powell, F.F., Robbing Peter to Pay Paul (download)

Augustine, On Christian Teaching