The Philistines seem to be speaking here. Alternate translation: "The Philistines say, 'Woe ... the sea.'" (See: [[rc://en/ta/man/translate/figs-explicit]])
Here Jeremiah is speaking. He continues speaking of the sword of Yahweh as if it were a person who could rest. Yahweh punishing the Philistines by sending the army of the north is spoken of as if Yahweh were striking the people with a sword. (See: [[rc://en/ta/man/translate/figs-personification]] and [[rc://en/ta/man/translate/figs-metaphor]])
Jeremiah uses a question to mean that the sword cannot stop since Yahweh has commanded it to continue killing. This question can be translated as a statement. Alternate translation: "It cannot stop, for Yahweh has commanded it" (See: [[rc://en/ta/man/translate/figs-rquestion]])