This Bible contradiction is from the Skeptic's Annotated Bible.
Matthew 11:13-14 View context
For all the prophets and the law prophesied until John.
And if ye will receive [it], this is Elias, which was for to come.
Matthew 17:12-13 View context
But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them.
Then the disciples understood that he spake unto them of John the Baptist.
Mark 9:13 View context
But I say unto you, That Elias is indeed come, and they have done unto him whatsoever they listed, as it is written of him.
John 1:21 View context
And they asked him, What then? Art thou Elias? And he saith, I am not. Art thou that prophet? And he answered, No.