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 a people prepared for the Lord."
In the spirit and power of Elijah ...  In these words, an angel of God explained what was meant by the promised coming of Elijah  (Malachi 4:5,6). The express terminology of Malachi's prophecy was used here by the angel; and, therefore, there was no excuse for the refusal of the Pharisees and other leaders of Israel to recognize John the Baptist as the fulfillment of Malachi's prophecy.  Not only was there this specific heavenly identification of the promised son as that "Elijah," but there was the additional fact of John's conformity to the pattern of clothing worn by the first Elijah.  Jesus, of course, confirmed the word of the angel, citing John the Baptist as the Elijah who was to come  (Matthew 17:9-13).