John 1:21

And they asked him, What then? Art thou Elijah? and he saith, I am not. Art thou the prophet? And he answered, No.

John the Baptist was called Elijah by Christ himself (Matthew 17:12), and this raises the question of why John here denied it. This is another example of the kind of "contradiction" which so delights some of the critics. Literally, John the Baptist was NOT Elijah, and John's literal answer WAS literally true. Typically and spiritually, John the Baptist was THAT Elijah foretold in Malachi 4:5; but there is no evidence that John the Baptist knew his own identity as that Elijah; and, if he did know it, his answer was still the truth. The angel's annunciation of the birth of John the Baptist had clearly linked the great herald with the promised return of Elijah, a fact which the Sanhedrin should have known, since the announcement was made in the temple itself and to one of their priests in the course of his solemn duties therein. However, the popular notion was that the original Elijah would rise from the dead; and, if John the Baptist had given an affirmative answer to their question, it would have been, in the context, a falsehood. Therefore, he denied that he was Elijah, in the sense in which the question had been asked. Thus, even if John the Baptist knew that he was "that Elijah," and it may be assumed that he did know it, the gross literalization of the promised return of Elijah in the popular mind would have made it impossible for him to have answered affirmatively.

Art thou the prophet? ... is a reference to the prophet like unto Moses (Deuteronomy 18:15-18) who must be identified with the Messiah. This question therefore covers the same ground as the query, "Art thou the Christ?" which had already been answered. It was the old reporter's trick of asking the same question again in different words, and John again answered it negatively.