וַיֹּֽאמְרוּ֙ דָּ֣ם זֶ֔ה הָחֳרֵ֤ב נֶֽחֶרְבוּ֙ הַמְּלָכִ֔ים וַיַּכּ֖וּ אִ֣ישׁ אֶת־רֵעֵ֑הוּ וְעַתָּ֥ה לַשָּׁלָ֖ל מוֹאָֽב׃
e disseram: Isto é sangue; certamente os reis pelejaram entre si e se mataram um ao outro! Agora, pois, à presa, moabitas!
Ibn Ezra
חרב יחרבו They will be slain. This verb is derived from חרב sword; comp. החרב נחרבו they are surely slain. (2 Kgs. 3:23). Some explain it they shall be utterly wasted, and compare it with חרבן destruction. I prefer the first explanation.