Gospel of Barnabas

Then Jesus said: "I am a voice that cries through all Judea, and cries: 'Prepare you the way for the messenger of the Lord', even as it is written in Esaias." They said: "If you be not the Messiah nor Elijah, or any prophet, wherefore do you preach new doctrine, and make yourself of more account than the Messiah?" Jesus answered: "The miracles which God works by my hands show that I speak that which God wills; nor indeed do I make myself to be accounted as him of whom you speak. For I am not worthy to unloose the ties of the hosen or the ratchets of the shoes of the Messenger of God whom you call 'Messiah', who was made before me, and shall come after me, and shall bring the words of truth, so that his faith shall have no end."
— Chapter 43

Muhammad as the Messiah

According to one version[specify] of the Gospel of Barnabas:

Then said the priest: "How shall the Messiah be called?" [Jesus answered] "Muhammed is his blessed name".
— Chapter 97

and

Jesus confessed, and said the truth: "I am not the Messiah."
— 42:2

Ishmaelite Messiah

According to one version of the Gospel of Barnabas, Jesus denied being the Messiah, claiming rather that the Messiah would be Ishmaelite (i.e. Arab):

Whereupon Jesus said: "Ye deceive yourselves; for David in spirit calleth him lord, saying thus: 'God said to my lord, sit thou on my right hand until I make thine enemies thy footstool. God shall send forth thy rod which shall have lordship in the midst of thine enemies.' If the messenger of God whom ye call Messiah were son of David, how should David call him lord? Believe me, for verily I say to you, that the promise was made in Ishmael, not in Isaac."

— Barnabas 43:10

The Gospel of Barnabas is fake and the earliest copy is in Italian from the year 1600 AD. There is virtually no evidence of it existing before medieval times.

https://www.catholic.com/magazine/online-edition/why-the-gospel-of-barnabas-is-a-medieval-fake
https://en.wikipedia.org/wiki/Gospel_of_Barnabas