Why is there a cry from Babylon?  

There is a passage of historical narrative at the end of the oracle against Babylon in Jeremiah 51:59–64. But the oracle itself ends with a passage of poetry in Jeremiah 51:54–58 that repeats many of the themes introduced in Jeremiah 50:2–3 and developed through the oracle. These themes give an emphatic finale to the Lord’s message of immanent judgment of Babylon. This is also the Lord’s message of assurance to the exiles in Babylon. A voice! A cry from Babylon. These are the desperate cries for help as Babylon is defeated. But this could also be a command for the exiles to listen and hear. The break-up of the land reverberates in the prophet’s ears as he presses upon his audience the certainty of what the Lord will do.¹ For the Lord is laying Babylon waste, and stilling her mighty voice. Their waves roar like many waters; the noise of their voice is raised. Babylon’s mighty voice is drowned out and overwhelmed by a louder, more powerful voice. The Lord is sending a destroyer that will come upon Babylon and defeat her for the Lord is a God of recompense; he will surely repay. The Hebrew phrase is el gemulot, meaning God of recompense. The Lord is the faithful covenant God who makes payment appropriately and in full.² The image of the Lord’s cup of wrath returns (see Jeremiah 25:15; Jeremiah 51:7; Jeremiah 51:39). The leaders and warriors of Babylon will be overcome by the Lord’s judgment, he will make them all drunk, leaving them powerless to defend the nation. There could also be an illusion again to the great feast that the king of Babylon hosted the night before Babylon fell (see Daniel 5:1–31).

The Lord, who is the true King over all nations, says that Babylon’s mighty walls will come crashing down and her high gates will be burned with fire. All Babylon’s impressive fortifications will prove ineffective against the invasion. The peoples labour for nothing, and the nations weary themselves only for fire. This is a well-known saying (see Habakkuk 2:13) and in this case it probably refers to the foreign nations that have worked hard to build the Babylonian empire. Their efforts have all gone up in fire.³ In a broader sense it also speaks of the futility of human effort in trying to resist the Lord and his purposes and that reality should feed the weak faith of the exiles in Babylon as they wait for the Lord to set them free and bring them home.