Malachi 4 is the last word of God in the Old Testament before 400 years of silence are broken by the angel Gabriel’s message to Zechariah in the temple, telling him that he would be the father of the one to prepare for the coming of the Messiah.
Malachi 4 contains a warning of coming judgment, both in the near and more distant future:
“Nor, again, have we any right to exclude the whole period from the destruction of Jerusalem till the last judgment, as if in the great book of history only the first and last leaf were written with the finger of God, and the rest left vacant.” (E. W. Hengstenberg, Christology of the Old Testament, on Malachi 4:1).
Geerhardus Vos notes (The Eschatology of the Old Testament, p. 162) regarding Malachi:
“The judgment aspect of Jehovah’s advent—the coming is condensed into the one ‘day’ par excellence and this one day assumed the character of a veritable dies irae (‘day of wrath’) (3:2; 4:1). . . . Side by side with this retributory aspect, the judgment assumes the form of a process of purification resembling the method whereby silver and gold are extracted from the dross adhering to them.”
“Malachi shows that despite God’s mercy in choosing Israel over Edom (1:1–5), Israel’s response to exhortations to faithfulness has been negative. . . . If Israel will repent of its many sins, God will bless the people again in the future (3:5–18). Judgment is coming, but the faithful will be spared (4:16).” G. K Beale, A New Testament Biblical Theology, p. 85).
From the Reflection for Trinity Presbyterian Church