Albert Barnes Commentary Malachi 3:5

"And I will come near to you to judgment; and I will be a swift witness against the sorcerers, and against the adulterers, and against the false swearers, and against those that oppress the hireling in his wages, the widow, and the fatherless, and that turn aside the sojourner [from his right], and fear not me, saith Jehovah of hosts." — Malachi 3:5 (ASV)

And I will come near to you to judgment - They had clamored for the coming of “the God of judgment”; God assures them that He will come to judgment, which they had desired, but far different from what they expect. The few would be purified; the great mass of them (so that He calls them “you”), the main body of those who had so clamored, would find that He came as a Judge, not for them but against them.

And I will be a swift witness - “In judging I will bear witness, and witnessing, I, the same, will bring forth judgment, says the Lord; therefore, the judgment will be terrible, since the judge is an infallible witness, whom the conscience of no one will be able to contradict.”

God would be a “swift witness,” as He had said before, “He shall come suddenly.” Our Lord calls Himself “the Faithful and True witness” (Revelation 3:14; Revelation 1:5; Theodoret and Jerome: “I, and not other witnesses, having seen with My own eyes.”) when He stands in the midst of the Church, as their Judge.

God’s judgments are always unexpected by those on whom they fall. The sins mentioned are those especially condemned by the law: the use of magical arts, as drawing men away from God, and the rest as sins of special malignity.

Magical arts were rife at the time of our Lord’s coming. Adultery was also common, as shown in the history of the woman taken in adultery, when her accusers were convicted by their own consciences (John 8:9; compare the phrase “adulterous generation,”Matthew 12:39).

Lightfoot, commenting on John 8:3, quotes Sotah f. 47.1: “From the time that homicides were multiplied, the beheading of the heifer ceased: from the time that adulterers were multiplied, the bitter waters ceased.” He also quotes Maimonides on Sotah, chapter 3: “When the adulterers multiplied under the second Temple, the Sanhedrin abolished the ordeal of the adulteresses by the bitter water, relying on its being written, ‘I will not visit your daughters when they commit whoredom, nor your spouses when they commit adultery.’”

Lightfoot adds, “The Gemarists teach that Johanan ben Zacchai was the author of that advice, who was still alive, in the Sanhedrin, and perhaps among those who brought the adulteress before Christ. For some things make it probable, that the ‘scribes and Pharisees,’ mentioned here, were elders of the synagogue.”

Justin Martyr reproaches them with having fresh wives wherever they went throughout the world (Dialogue with Trypho, concluding section, page 243, Oxford translation).

Oppress the hireling - literally “oppress the hire,” that is, deal oppressively in it. “Behold,” says James (James 5:4), “the hire of the laborers who have reaped down your fields, which is by you kept back by fraud, crieth; and the cries of them which have reaped are entered into the ears of the Lord of Sabaoth.” The mere delay in the payment of the wages of the laborer brought sin upon him, against whom he cried to God (Deuteronomy 24:14–15). It is no light sin, since it is united with the heaviest, and is spoken of as reaching the ears of God. The widow and the fatherless stand in a relation of special nearness to God.

And fear not Me - He closes with the central defect, which was the mainspring of all their sins: the absence of the fear of God. The commission of any of these sins, rife as they unhappily are, proves that those who committed them had no fear of God. “Nothing hinders that this should be referred to the first coming of Christ. For Christ, in preaching to the Jews, exercised upon them a judgment of just rebuke, especially of the priests, Scribes and Pharisees, as the Gospels show.”