The word "sword" refers to Judah's enemies. Also, the word "devour" compares Judah's enemies coming to kill them to a wild animal that attacks and eats other animals. AT: "your enemies will kill you" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])
The word "mouth" emphasizes that Yahweh has spoken and what he says will certainly happen. AT: "Yahweh has spoken" or "Yahweh has said that this will happen" (See: [[rc://en/ta/man/translate/figs-synecdoche]])