John Wesley on 2 Kings 3:9

King of Edom - That is, the vice - roy under Jehosaphat, 1Kings 22:47, here called king: because that word is sometimes used for any prince or chief ruler. Seven days - Because they made a great army, which could move but slowly; and they fetched a greater compass than was usual, for some advantage which they expected by it. No water - A frequent want in those parts; and now, it seems, increased by the extraordinary heat and dryness of the season.