Albert Barnes Commentary Zechariah 14:12

"And this shall be the plague wherewith Jehovah will smite all the peoples that have warred against Jerusalem: their flesh shall consume away while they stand upon their feet, and their eyes shall consume away in their sockets, and their tongue shall consume away in their mouth." — Zechariah 14:12 (ASV)

Again, upon the restoration of His people follows the destruction of His enemies. It shall, first and chiefly, be God’s doing, not man’s. This shall be the plague. The word is used of direct infliction by pestilence, wherewith the Lord shall smite all the people (peoples) that fought against Jerusalem. The awful description is of living corpses. Lap.: “The enemies of Jerusalem shall waste, not with fever or disease, but by a plague from God, so that, being sound, standing, living, in well-being, they should waste and consume away,” as Isaiah speaks of the carcasses of the men, that have transgressed against Me; for their worm shall not die - and they shall be an abhorring unto all flesh (Isaiah 66:24).

Their flesh shall consume away - Rather, “wasting away the flesh of each one.” It is the act of God, in His individual justice to each one of all those multitudes gathered against Him. One by one, their eyes, of which they said, let our eye look on Zion (Micah 4:11), that is, with joy at its desolation, shall consume away in their holes, and their tongue, with which they blasphemed God, shall consume away in their mouths (Isaiah 36:15, 36:18; Isaiah 37:3–4, 37:17, 37:23, 37:29). Appalling, horrible, picture! standing on their feet, yet their flesh mouldering away as in a graveyard, their sightless eyeballs decaying in their holes, the tongue putrefying in their mouth, a disgust to themselves and to others! Yet what, compared to the horrible inward decay of sin, by which men have a name that they live and are dead? (Revelation 3:1).

Jerome: “Let us read Ecclesiastical histories, what Valerian, Decius, Diocletian, Maximian, what the most savage of all, Maximin, and lately Julian suffered, and then we will prove by deeds, that the truth of prophecy was fulfilled in the letter also.”