As mentioned at the beginning of this chapter in the discussion of its structure, there is no reason for starting a new paragraph with this verse. The verse is better understood as taking up again the battle scene of verses 2-3, and explaining the means by which the LORD will defeat those nations who are attacking Jerusalem.
And this shall be the plague: This refers forward to something that is to follow, namely the description of medical symptoms in the second half of the verse. The term plague (Good News Translation “a terrible disease”) is used in the sense of an epidemic though the details that follow do not match any condition identifiable to modern medicine. It is used elsewhere for instance in Num 14.37; Num 16.46-50; 2 Sam 24.21, 25. In the context of the defeat of the enemies of God’s people, the prophet probably also has in mind such passages as 2 Kgs 19.35 (where Sennacherib’s army was miraculously destroyed) and Ezek 38.21-22 (where the forces of Gog are overcome), though the same word does not occur in them.
With which the LORD will smite all the peoples that wage war against Jerusalem: The word smite is an old-fashioned term in English, which New Revised Standard Version replaces with the modern word “strike.” Good News Translation avoids the rather awkward relative clause in Revised Standard Version here, and says, “The LORD will bring a terrible disease on….” All the peoples that wage war against Jerusalem refers to the same type of groups as those mentioned in verses 2 and 3. The present verse gives a detailed picture of how the LORD will “fight against” them (verse 3). It is not made clear until verse 16 that although every nation among the enemy forces will be affected by the plague, not every individual person will be.
Their flesh shall rot while they are still on their feet: In Hebrew their is actually a singular possessive suffix, referring to individuals distributively. Most English versions translate it as plural since this is the more natural way to express the meaning in English. Translators should use whichever form is more natural in their language. The disease that the LORD sends will be so terrible that people will be like living corpses (New Living Translation “walking corpses”). In this context flesh is literal and refers to the softer parts of the human body as opposed to the harder parts like bones. This material will rot or decay while the enemy are still on their feet. In contrast to the course of a normal illness, in which people feel unwell but have time to go and lie down, the plague that is the LORD’s punishment will afflict the enemy suddenly in the midst of their normal duties. Good News Translation “while they are still alive” fails to capture this element of suddenness. Another way to express the meaning is “while they are still standing upright,” or as Contemporary English Version “While they are standing there.” The mention of feet in Hebrew is perhaps a contrasting echo of the mention of the LORD’s feet in verse 4.
Their eyes shall rot in their sockets: The first occurrence of their refers to the enemy, whereas the second refers to the eyes. In Hebrew the distinction is quite clear because the possessive suffixes are of different genders. In some languages translators may need to use a different term to describe eyes rotting from the term used to describe flesh rotting (Die Bibel im heutigen Deutsch).
Their tongues shall rot in their mouths: The enemy will be deprived not only of sight but also of speech. Some versions like Good News Translation combine the last two clauses into one: “their eyes and their tongues will rot away.” This does not omit any of the elements of the meaning, but it does lose some of the cumulative effect of having three parallel clauses. Translators are recommended to keep three clauses unless there are very strong reasons for doing otherwise. Contemporary English Version has “he will make their flesh rot and their eyes fall from their sockets and their tongues drop out.”
Quoted with permission from Clark, David J. & Hatton, Howard A. A Handbook on Zechariah. (UBS Helps for Translators). New York: UBS, 2002. For this and other handbooks for translators see here .