“Cursed be

The one

Who is slack

In doing

The work of Yahweh!

Cursed be

The one

Who keeps back

The sword

From bloodshed.”

Jeremiah seems to indicate here that you should not be slack in doing the work of Yahweh. Since the work of Yahweh here is killing the Moabites, holding back your sword from bringing bloodshed would mean that you would be cursed also.