Following the painful lament over the fall of Jerusalem, a fierce cry emerges for historical justice against the empire responsible for the ruin. The plea is directed at the Babylonian kingdom, carrying a heavy curse and a deep prayer for its ultimate downfall [אבן עזרא, מאירי]. The reference to the nation encompasses both the people of Babylon and its ruling power [רד״ק, מצודת ציון].
The exact state of Babylon in this plea is viewed in a few different ways. The primary approach among commentators is that its impending doom is so certain that it is spoken of as if it has already happened, utilizing a common prophetic style to describe a guaranteed future ruin [רד״ק, מצודת דוד, מאירי]. Alternatively, rather than looking at a future punishment, this description might highlight Babylon's active role as an empire that constantly robs, plunders, and destroys other nations [ביאור שטיינזלץ, מצודת ציון]. A third perspective suggests that the destruction had already begun under Cyrus, and the prayer is simply a request for that downfall to be brought to its absolute completion [מלבי״ם].
There is a deep longing that whoever finally repays Babylon for what it did to Israel will be praised and glorified. Historically, this avenger is identified as Darius the Mede, who ultimately brought about Babylon's collapse [רד״ק, מצודת דוד, מאירי]. The intensity of the desired revenge stems directly from the horrific physical cruelty the Babylonians inflicted upon Israel during the destruction [תורה תמימה].
The demand that Babylon be paid back in full carries several layers of meaning. It is a call for justice against the very initiation and execution of their evil [מצודת ציון]. Beyond the physical acts, the destruction of Jerusalem was driven by a burning, deeply emotional hatred. Therefore, the prayer asks that the Babylonians suffer a punishment fueled by that exact same measure of hatred and vengeance [מלבי״ם]. On a deeper level, Babylon did not merely attack the people of Israel; they offended the honor of God. The call for retribution is thus a demand for justice on behalf of heaven itself [אלשיך].
A historical difficulty arises regarding this justice, as many of the actual soldiers who destroyed Jerusalem died natural deaths during the seventy years of exile, leaving only their descendants to suffer Babylon's eventual fall. To resolve this, there is a belief that in the future, God will bring those historical destroyers back to life. This ensures they will personally experience their fitting punishment right before the eyes of the very people they tortured [אלשיך].