Thomas Aquinas Commentary Lamentations 4:21

"Rejoice and be glad, O daughter of Edom, that dwellest in the land of Uz: The cup shall pass through unto thee also; thou shalt be drunken, and shalt make thyself naked." — Lamentations 4:21 (ASV)

Here, the prophet threatens those who are insulting them, and especially the Edomites.

The prophet does two things: first, he threatens them; second, he consoles the Jews, saying, your iniquity is accomplished (Lamentations 4:22).

Regarding the threat, he first excludes their joy by saying mockingly, rejoice. This is like the lament, Tell it not in Geth, publish it not in the streets of Ascalon (2 Samuel 1:20). The phrase Daughter of Edom refers to the people of the Edomites, who are in the land of Hus.

An objection is then raised concerning this location. Deuteronomy 2:5 states, I have given Mount Seir to Esau for a possession, and Genesis 22:21 notes that Hus was the firstborn of Nahor.

However, the text is not speaking about the man named Hus, but about the land called Hus, which is also known as Ausitis, as the Gloss says.Jerome, In Hieremiam prophetam libri vi 5.308 (CSEL 59.308; PL 24:679 [705]). This is supported by Jeremiah 25:20, which mentions all the kings of the land of Ausitis, a region on the border of the Edomites and the Arabs.

Second, he threatens punishment. The phrase to you also shall the cup come signifies the wrath of God. You shall be made drunk means you will be filled with misery, and and naked means you will be stripped of all your goods. This is confirmed in Jeremiah 49:12: Behold they whose judgment was not to drink of the cup, shall certainly drink.