Elijah who was to come = John the Baptist


Luke 1:17
And he shall go before him in the spirit and POWER, ("DUNAMIS" #1411), 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.
Elijah & John the Baptist have this in common: they both took on their faithless nation, calling them from the most heinous rebellion, singlehandedly. This required unusual faith. They both were granted the Spiritual Gift of Faith (1 Cor 12:9) which lasts for the situation needed, but the man is left afterward with his own regular faith. This Gift of Faith enabled Elijah to single-handedly confront the 450 prophets of Baal in 1 Kings 18:22-45. But immediately following, his own faith was not enough to stand up to a lone woman named Jezebel: Elijah ran from her for his life (1 Kings 19:1-3). Likewise, John the Baptist was granted the Gift of Faith to single-handedly stand against the broods of vipers of Pharisees & Sadducees and single-handedly identifying boldly to the world that Jesus is the Son of God, the Christ, the Lamb of God (Matthew 3:1-16 and John 2:15-32). But later, when this Gift of Faith had served its purpose, John the Baptist had to send messengers to find out if Jesus was, in fact, the One who was to come (Luke 7:20). John the Baptist did no miracles (John 10:41), but Elijah did (1 Kings 17:1 and 1 Kings 17:13-22 and 1 Kings 18:1 and 1 Kings 18:41-45 and 1 Kings 19:7 and 2 Kings 1:10-16 and 2 Kings 2:7-11). The spirit and POWER, ("DUNAMIS" #1411), of Elijah which John the Baptist shared was the spiritual Gift of Faith (1 Cor 12:9) which gave them temporary, supernatural Faith to withstand far more than they could have on their own faith.
1 Corinthians 12:7-9
7 But the manifestation of the Spirit is given to every man to profit withal.
8 For to one is given by the Spirit the word of wisdom; to another the word of knowledge by the same Spirit;
9 To another faith by the same Spirit; ...
"To another," indicates here, as in the rest of the passage, that it is a special Gift that is not given to everyone all the time. It is the spiritual Gift of [Special] Faith temporarily, miraculously added to one's personal faith.