Thomas Aquinas Commentary Jeremiah 6:22-26

"Thus saith Jehovah, Behold, a people cometh from the north country; and a great nation shall be stirred up from the uttermost parts of the earth. They lay hold on bow and spear; they are cruel, and have no mercy; their voice roareth like the sea, and they ride upon horses, every one set in array, as a man to the battle, against thee, O daughter of Zion. We have heard the report thereof; our hands wax feeble: anguish hath taken hold of us, [and] pangs as of a woman in travail. Go not forth into the field, nor walk by the way; for the sword of the enemy, [and] terror, are on every side. O daughter of my people, gird thee with sackcloth, and wallow thyself in ashes: make thee mourning, as for an only son, most bitter lamentation; for the destroyer shall suddenly come upon us." — Jeremiah 6:22-26 (ASV)

1. Here, he describes the coming of the enemy explicitly.

First, he describes the nature of the enemy.

Second, the incorrigibility of the people, as in I have set you as an assayer over my people, a stronghold (Jeremiah 6:27).

Concerning the first point, there are three things.

1. He describes the enemies as strong because of their number (a great nation) and their weapons (the arrow). They are cruel—cruel like the sea—so that they terrify by their sound and their purpose: and they will ride on horses, prepared as a man for battle. As it says below: behold, a people will come from the north, and a great nation, and many kings will arise from the ends of the earth. They will take up bow and shield; they are cruel and merciless (Jeremiah 50:41–42).
2. He speaks of the Jews’ fear of their reputation: we have heard the report of it; our hands have become weak. We are able to do nothing because of fear. Fear seized them there, pains as a woman in labor (Psalms 47:7). The effect of this fear is: do not go out. Outside, the sword will lay them waste, and inside, fear (Deuteronomy 32:25).
3. He urges them to accept the pain of repentance: O daughter of my people, gird yourselves with sackcloth. As it says above: for this gird yourselves with sackcloth... and wail, because the wrath of the Lord’s fury has not turned back from us (Jeremiah 4:8).