"Leb Kamai" is a cryptogram for Chaldea which is Babylon. Even though Babylon was the "gold cup" of judgment from which God made the whole earth drink (Jeremiah 25:15-29; Revelation 17:3-4; 18:6), they would experience judgment through the king of the Medes (539 B.C. by Darius [Daniel 5:31] and subsequent kings). God's vengeance was strong because of "all the wrong they had done in Zion" (51:24) by destroying the temple of God (50:28).
Jeremiah 51:15-19 are almost synonymous with 10:12-16 where Jeremiah speaks of God's sovereignty and power.
In this chapter, he summons the three warlike nations of Ararat (present-day Armenia), Minni (Western Iraq), and Ashkenaz (near the previous two) to lay waste the land of Babylon.
Jeremiah sent this message via Seraiah who was a staff officer to the king, cared for the comforts of the army, and was probably the brother of Baruch, Jeremiah's scribe (32:12). The scroll was to be tied with a stone and thrown into the Euphrates to announce that Babylon, like the scroll, would sink and rise no more (Revelation 18:21).
These were Jeremiah's final words!
Even though God used an evil empire to bring judgment upon His people, he would not let the evil of that empire go unpunished. The guilty will not go unpunished, and we must trust in His sovereignty, power, and justice.
Meditate on the sovereignty and power of God by praying through 51:15-19 below!
It is He who made the earth by His power,
Who established the world by His wisdom,
And by His understanding He stretched out the heavens.
When He utters His voice, there is a tumult of waters in the heavens,
And He causes the clouds to ascend from the end of the earth;
He makes lightning for the rain
And brings forth the wind from His storehouses.
All mankind is stupid, devoid of knowledge;
Every goldsmith is put to shame by his idols,
For his molten images are deceitful,
And there is no breath in them.
They are worthless, a work of mockery;
In the time of their punishment they will perish.
The portion of Jacob is not like these;
For the Maker of all is He,
And of the tribe of His inheritance;
The Lord of hosts is His name."