What does Malachi 4:6 mean?
Revelation 11:1–13 describes an event, during the end times, when two witnesses will preach against Antichrist, and this will cause many people to repent. Malachi 4:5 predicted the eventual return of Elijah, which Christians typically interpret as a separate instance from the messenger predicted in Malachi 3:1. Jesus, speaking after the death of John the Baptist, said that Elijah was yet to come (Matthew 17:11). So, many people believe that these two witnesses will be Moses and Elijah (Matthew 17:1–3). However, they might not be specifically connected to this particular prophecy, and John the Baptist might well have been the complete fulfillment of this prediction.The ending phrase of this verse is either translated as "curse," or "destruction." This is an incredibly potent Hebrew word: he'rem. This is the term used in Joshua 6:17–18 to describe God's decree for the complete and utter annihilation of Jericho. Cities or people under he'rem, or "the ban," or "the curse," were those assigned to total destruction, with nothing to be spared, captured, or kept. The same term, with the same meaning, is used in 1 Samuel chapter 15 in reference to the Amalekites.
Both in Hebrew and in English, "he'rem / curse / destruction" is the final word in this verse. And so, the very last word of the Old Testament is a warning about utter and total obliteration. The same destruction God reserved for a very few rare instances in history is now looming over Israel's head. The dire consequences of ignoring God, paired with a promise of His mercy, is God's sign off for the entire Hebrew Scriptures.
That the words of verses 4, 5, and 6 are the last prophetic message given to Israel makes them especially poignant. God would not send a prophet again until John the Baptist, some four centuries later. This message is also a foreshadowing of the structure of the New Testament. The last message of the Old Testament ends with a warning about an impending day of judgment. Likewise, Revelation, the last message of the New Testament, is about the end times and God's time of ultimate reckoning.