a) The Centenary Jubilee
In the time of Moses God ordained that the Jews were to observe a jubilee year twice a century:
Throughout the centuries this command was observed and the Roman Catholic Church eventually took it over into the Christian faith. About 1300 AD Pope Boniface the Eighth gave a decree that the jubilee should be observed once every hundred years. This is the only occasion in all history that the jubilee year was made to be only once every hundred years. After the death of Boniface, however, Pope Clemens the Sixth decreed in 1343 AD that the jubilee year should revert to once every fifty years as it was observed by the Jews after the time of Moses. Now we find in the Gospel of Barnabas that Jesus is alleged to have said:
Only one solution can account for this remarkable coincidence. The author of the Gospel of Barnabas could only have quoted Jesus as speaking of the year of jubilee as coming “every hundred years” if he knew of the decree of Pope Boniface. But how could he know of this decree unless he lived at the same time as the Pope or sometime afterwards? This is a clear anachronism which compels us to conclude that the Gospel of Barnabas could not have been written earlier than the fourteenth century AD.
This also means that the Gospel of Barnabas dates at least seven hundred years after the time of Muhammad and it is in the circumstances of no historical value at all. Although it often makes Jesus predict the coming of Muhammad by name (which is why it is a best-seller in the world of Islam today), as it was written after the death of Muhammad, these “prophecies” are of no interest or value at all. Indeed the Gospel of Barnabas contains many discourses and practices fully synonymous with the basic teachings of Islam - but these too are of no value because the book was written at least seven hundred years after the advent of Islam.
Prophecies that are first composed centuries after the event they foretell has come to pass are of no more interest or value than yesterday's weather forecast. We conclude, from the striking quote about the jubilee year, that the author of the Gospel of Barnabas wrote his book not earlier than the fourteenth century after Christ. Let us press on to examine further evidence of mediaeval features.