Question 260: What Is Meant By: “This Is Elijah Which Was To Come?”
Answer:
There was a prophecy that YHVH would send Elijah or Elisha to turn the hearts of the people (Malachi 4:5). When John appeared, the Jews asked him if he was Elijah and he answered that he was not (John 15:21). They evidently expected that the literal Elijah, who is represented as ascending to heaven without dying (2 Kings 2:11), would be sent to earth. John knew he was not that He regarded himself as a humble messenger, a mere voice, with no distinction but that of preparing the way. The character of his preaching however shows that, like other messengers from YHVH, he underestimated his dignity. When Moshiach spoke of him He settled the question definitely in the passage you refer to. John, He said, was the Elijah to whom the prophecy referred.