John the Baptist was a fulfillment of the
prophecy. The angel spoke to Zacharias,
the father of John the Baptist, saying,
"And he shall go before him in the spirit
and power of Elias, to turn the hearts of
the fathers to the children, and the
disobedient to the wisdom of the just; to
make ready a people prepared for the Lord."
Luke 1:17

This is a definite reference to the prophecy
in Malachi 3:4-5, but it also tells us that
John the Baptist was not Elijah personally,
but would come in the 'spirit and power of
Elias'.