Its just Apocrypha. There are lots of them that surface from time to time—Like the Gospel of Judas, or the Gospel of Pontius Pilot. What IS the verses that seem to imply a coming of Mohammed? It might refer to many other things or saints.
Lot of social mobility in those days. He rose through the ranks from river pilot to Governor of Judea. No wonder he got his own gospel.
Several articles on the so called “Gospel” of Barnabas...
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1) The Gospel of Barnabas; a Muslim forgery
http://www.letusreason.org/Apolo34.htm
2) The Gospel of Barnabas; a Muslim forgery Part 2
http://www.letusreason.org/Apolo35.htm
3) What do we know about the Gospel of Barnabas?
http://answering-islam.org/Barnabas/
4) The Forgery of the Gospel of Barnabas
http://www.muslimhope.com/ForgeryOfTheGospelOfBarnabas.htm
5) What about the Gospel of Barnabas? Who wrote it and why? Was he an apostle?
http://www.evidenceforchristianity.org/index.php?option=com_custom_content&task=view&id=4506
That was my question. The verses that refer to the Holy Spirit seem the only ones, but they have to be twisted in ways that I cannot wrap my mind around.