Speaking of John the Baptist, Jesus said, “If you are willing to accept it, he is Elijah, the one who is to come. “
What brought that on was that the people had been aware of the prophecies of Malachi, the very last of the prophets. The following is the last verse of the Old Testament in of our Bibles. Malachi wrote,
“Lo, I will send you Elijah, the prophet, before the day of the Lord comes, the great and terrible day.”
People who knew about that prophesy were saying Jesus could not be the Messiah, because the Bible said Elijah must come first.
Then, people began saying that perhaps John the Baptist was Elijah come back with another name. When the Apostles asked Jesus about that, he gave the answer that he was Elijah “If you are willing to accept it.”