The Messiah would be preceded by a messenger
Malachi 3:1 reads:
“Behold, I send my messenger, and he will prepare 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.”
Both Malachi 3:1 and Isaiah 40:3 speak of someone coming to “prepare the way” of the Lord, using the same Hebrew phrases. (See commentary on Isaiah 40:3.) They differ in that Malachi speaks of a messenger coming to prepare the way, while Isaiah speaks of preparing the way in the desert.
Malachi is speaking to Jewish people who had returned to the land of Israel from exile in Babylon and who had rebuilt the temple. Yet the promises of God’s glory filling the temple had apparently not materialized. To a dispirited people, Malachi prophesies that God will indeed come to the temple, preceded by a “messenger.”
What then did you go out to see? A prophet? Yes, I tell you, and more than a prophet. This is he of whom it is written, ‘Behold, I send my messenger before your face, who will prepare your way before you.’
One thing that is significant here, is that in Malachi, God says the messenger will “prepare the way before me,” whereas Matthew and its parallel in Luke have “before you,” referring to Jesus himself. In this passage in Matthew and in Luke, what applied to God in Malachi is applied to Jesus! (It was not uncommon to cite Scripture with variations, just as a modern preacher might paraphrase a bit in order to make a point.)
Mark 1:2-3 combines Malachi 3:1 and Isaiah 40:3, though he only mentions Isaiah by name. It was customary to often cite several Scriptures with similar phraseology but only mention the leading prophet; readers and listeners knew their Bible and would know which was which.
As it is written in Isaiah the prophet, “Behold, I send my messenger before your face, who will prepare your way, the voice of one crying in the wilderness: ‘Prepare the way of the Lord, make his paths straight.’”
Mark immediately goes on to talk about John the Baptist as the “messenger” of Malachi and the “voice” of Isaiah.
While Matthew, Mark, and Luke all speak of John as the preparer in the context of his ministry as an adult, Luke also speaks of him the same way, but at his birth. He may be alluding to either Malachi 3:1 or Isaiah 40:3; there’s not enough information to tell which. But we see the full context in Luke 1:76-79:
And you, child, will be called the prophet of the Most High; for you will go before the Lord to prepare his ways, to give knowledge of salvation to his people in the forgiveness of their sins, because of the tender mercy of our God, whereby the sunrise shall visit us from on high to give light to those who sit in darkness and in the shadow of death, to guide our feet into the way of peace.
In Luke, we see the big picture: when John prepares the way for Jesus, this will lead to salvation, forgiveness, light, and peace. This was some messenger!
And what about Malachi’s prophecy that God would come to his temple? The glory of God was shown in a climactic way when Jesus came to the temple (on several occasions in the Gospels), for in him the glory of God was revealed. We also see a glimpse of Jesus bringing God’s glory into the temple in Luke 2:25-32:
Now there was a man in Jerusalem, whose name was Simeon, and this man was righteous and devout, waiting for the consolation of Israel, and the Holy Spirit was upon him. And it had been revealed to him by the Holy Spirit that he would not see death before he had seen the Lord’s Christ. And he came in the Spirit into the temple, and when the parents brought in the child Jesus, to do for him according to the custom of the Law, he took him up in his arms and blessed God and said, “Lord, now you are letting your servant depart in peace, according to your word; for my eyes have seen your salvation that you have prepared in the presence of all peoples, a light for revelation to the Gentiles, and for glory to your people Israel.”
Above all, when Jesus was resurrected from the dead, God’s glory was revealed in the very body of Jesus, which he himself described as a temple:
Jesus answered them, “Destroy this temple, and in three days I will raise it up.” The Jews then said, “It has taken forty-six years to build this temple, and will you raise it up in three days?” But he was speaking about the temple of his body. When therefore he was raised from the dead, his disciples remembered that he had said this, and they believed the Scripture and the word that Jesus had spoken.