Matthew Poole and continuators on 2 Kings 3:8

8 And he said, Which way shall we go up? And he answered, The way through the wilderness of Edom .

Either, Iehoshaphat: or rather, Ioram: for the following answer may seem to be Iehoshaphat's.

Which though it was much the longer way, yet they thought it best; partly, to secure the King or Vice-Roy of Edom, of whom they might have some suspition, from that passage 2 Chron. 20. 22. and to carry both him and his Soldiers along with them into the War, both to get their assistance, and to prevent them from making a War of diversion against Iudah, whilst Iehoshaphat was engaged against Moab; and partly, that they might invade Moab on their weakest side, and where they least expected them. God also thus disposed their hearts to make way for the following miracle.