Luke 1:17 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.
The angel Gabriel continues his prophecy of Zechariah’s son, John the Baptist.
Look carefully, he (John the Baptist) will come before the Messiah. John the Baptist is not Elijah. John comes in the spirit and power of Elijah.
Later, Jesus Himself would confirm that John the Baptist functions as if Elijah.
Matthew 11:14 “And if you are willing to accept it, John himself is Elijah who was to come.” –Jesus.
John’s purpose is to make ready for the Lord a people prepared.
As Gabriel stated previously, the ministry of John the Baptist will associated with joy, gladness, and the grace of God. People will turn back to the Lord. This is the Hebraic concept of Teshuvah.

John the Baptist is associated with the first coming of Christ. Elijah is associated with the second coming.
In both the first and second comings of Jesus, the two forerunners to Christ will change the hearts of children and fathers.
Compare Gabriel’s comments to Malachi 4:5-6. These are the last words of the Old Testament. From Gabriel back to Malachi, it had been approximately 425 years since God had communicated with the Jewish people.
Malachi 4:5-6 Behold, I will send you Elijah the prophet before the great and awesome day of the LORD comes. He will restore the hearts of the fathers to their children and the hearts of the children to their fathers, so that I will not come and smite the land with a curse.
Elijah’s purpose… so that I will not come and smite the land with a curse.
When Elijah comes a second time, he will precede the second coming of Christ. His ministry will be associated with the great and awesome day of the LORD.
Although he is not specifically named, Elijah is likely one of the two witnesses in Revelation 11. The skill set and characteristics of the witnesses are consistent with the prophet Elijah on his first mission.
See 1 Kings 17-21 and 2 Kings 1-2 for Elijah’s initial career and efforts.
Revelation 11:3 And I will grant authority to my two witnesses, and they will prophesy for twelve hundred and sixty days, clothed in sackcloth.
Elijah will be dressed in sackcloth. These garments are made of a coarse, dark cloth from a goat. In Elijah’s day, sackcloth was worn in times of mourning, distress, mortification, or penitence.
Elijah promises fire, drought, water to blood, and all kinds of plagues.
Elijah will be an instrument of judgment.