Of all the Messianic prophecies mentioned, the New Testament places an emphasis on two prophecies, one from Malachi and the other from Isaiah, which foretell the forerunner to the Messiah. Although separate prophecies, they appear to be understood synonymously as one and appear more than once in all four gospels.

From his earliest introduction, John the Baptist is divinely revealed as a fulfillment of Malachi's prophecy of Elijah (Mal 3:1-3; 4:5-6); it is an angel who announces to Zacharias that his son will be a prophet in the spirit and power of Elijah (Luke 1:13-17).

For Zacharias, a priest (Luke 1:8-9), this association to Elijah (Mal 3:1-3; 4:5-6) would have been mind boggling, because Elijah was known for his spectacular work against 450 prophets of Baal and the 400 prophets of Asherah (1 Kings 18:19-40) that demonstrated the reality of God and brought people back to God. Also, it was well known among the priesthood that Malachi was the last genuine prophet of the Old Testament tradition, roughly 450 years ago, and the angel quoted portions of Malachi's prophecy to indicate the divine purpose of John the Baptist.

But the angel said to him, "Do not be afraid, Zacharias, for your petition has been heard, and your wife Elizabeth will bear you a son, and you will give him the name John. You will have joy and gladness, and many will rejoice at his birth. For he will be great in the sight of the Lord; and he will drink no wine or liquor, and he will be filled with the Holy Spirit while yet in his mother's womb. And he will turn many of the sons of Israel back to the Lord their God. It is he who will go as a forerunner before Him in the spirit and power of Elijah, to turn the hearts of the fathers back to the children, and the disobedient to the attitude of the righteous, so as to make ready a people prepared for the Lord." (Luke 1:13-17)

Malachi's prophecy addressed the nation of Judah almost 100 years after their return from Babylonian Captivity when Nehemiah was rebuilding of Jerusalem's walls. Reminding them of God's love and covenant fidelity (Mal 1:2-5), Malachi rebuked the nation of Israel for their shallow worship practices and that discipline will ensue with the coming Messiah who will judge and purify His people.

Behold, I am going to send My messenger, and he will clear the way before Me. And the Lord, whom you seek, will suddenly come to His temple; and the messenger of the covenant, in whom you delight, behold, He is coming," says the Lord of hosts. But who can endure the day of His coming? And who can stand when He appears? For He is like a refiner's fire and like fullers' soap. He will sit as a smelter and purifier of silver, and He will purify the sons of Levi and refine them like gold and silver, so that they may present to the Lord offerings in righteousness. (Mal 3:1-3)

Behold, I am going to send you Elijah the prophet before the coming of the great and terrible day of the Lord. 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. (Mal 4:5-6)

In the Old Testament, the phrase "Day of the Lord" was used to place an emphasis on the swift and decisive nature of God's victory over His enemies, and in the context of Israel, it was used to bring His people back into their covenant relationship with Him. However, Malachi's references to the "Book of Remembrance" (Mal 3:16-18) and imagery of judgment indicate that the "Day of the Lord" is about Jesus and Final Judgment (Rev 20:11-15). When Jesus arrives, He omits the phrase "Day of the Lord" and instead only speaks of the "Day of Judgment," and it is directed towards unrepentant non-Believers and in the context of Final Judgment (Matt 10:14-15; 11:20-24; 12:33-37; Luke 10:10-16).

The divine purpose of John the Baptist was to "clear the way" before the Messiah who will "restore the hearts" of Israel back to God. When his son was born, Zacharias spoke of his son as a prophet of the Old Testament tradition and prophetically explained what it meant to "clear the way":

And you, child, will be called the prophet of the Most High;
For you will go on before the Lord to prepare His ways;
To give to His people the knowledge of salvation
By the forgiveness of their sins,
Because of the tender mercy of our God,
With which the Sunrise from on high will visit us,
To shine upon those who sit in darkness and the shadow of death,
To guide our feet into the way of peace." (Luke 1:76-79)

Calling for repentance and forgiveness, John the Baptist testified of the coming Messiah and the kingdom of God (Matt 3:1-12; Mark 1:1-8; Luke 3:1-16; John 1:6). By giving "God's people the knowledge of salvation," it is the earliest form of the gospel. Luke characterized John the Baptist's teaching as "he preached the gospel to the people" (Luke 3:18), and for his exhortations, he was held in high esteem (Matt 14:5; 21:26; Luke 20:6). However, John the Baptist did not see himself as a prophet like Elijah; instead, he sees himself as a fulfillment of a prophecy of comfort from Isaiah, which is recorded in all four gospels. The gospel text in bold matches the bold text of Isa 40:1-5 seen below:

Isaiah prophesized for about 40 years (approximately: 740-701 B.C.) in his attempts to turn Judah back to God. Following his section of historical narratives (chapters 36-39), Isaiah begins his prophetic section of Israel's deliverance and glorious future, which academic theologians see as being addressed to Judah's future state of Babylonian Captivity. Although this event would take place some 200 years after Isaiah, his prophetic words of comfort were intended to encourage God's people to persevere in their faith with an expectation of the Lord's return.

Within the prophetic context of Malachi and Isaiah, John the Baptist is portrayed as a rebuke to Israel's covenant infidelity and a comfort because the Messiah is coming.

Proclaiming John the Baptist as the greatest of all prophets (Matt 11:7-14; Luke 7:26-28), Jesus quotes a part of Malachi's prophesy associating him as the forerunner to the Messiah and names him the "Elijah who was to come" (Matt 11:14; Mark 9:12-13). John the Baptist was fearless in his preaching about repentance and the coming kingdom of God (which was uniquely different from what Pharisees were teaching) in preparing people for the coming Messiah.

Because of Malachi's prophecy, John the Baptist's testimony identifying Jesus as the Messiah was validated (John 1:29-34; 3:27-36); no other human testimony had this authority.

To the Jews in Jerusalem challenging His claim of being the Son of God, Jesus presents the testimony of John as one piece of evidence.

If I alone testify about Myself, My testimony is not true. There is another who testifies of Me, and I know that the testimony which He gives about Me is true. You have sent to John, and he has testified to the truth. But the testimony which I receive is not from man, but I say these things so that you may be saved. He was the lamp that was burning and was shining and you were willing to rejoice for a while in his light. (John 5:31-35)

To the genuine Old Testament Believer, John the Baptist's testimony was instrumental to the calling of Jesus' first disciples (John 1:35-42).