“Behold, I will send you Elijah the prophet before the great and awesome day of the LORD comes.
and he will go before him in the spirit and power of Elijah, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just, to make ready for the Lord a people prepared.”Luke 1:17 ESV
and if you are willing to accept it, he is Elijah who is to come.Matthew 11:14 ESV