Adam Clarke's Commentary on the Bible

Verse 2 (Joel 3:2)

The valley of Jehoshaphat - There is no such valley in the land of Judea; and hence the word must be symbolical. It signifies the judgment of God, or Jehovah judgeth; and may mean some place (as Bp. Newcome imagines) where Nebuchadnezzar should gain a great battle, which would utterly discomfit the ancient enemies of the Jews, and resemble the victory which Jehoshaphat gained over the Ammonites, Moabites, and Edomites, 2 Chronicles 20:22-26 .

And parted my land - The above nations had frequently entered into the territories of Israel; and divided among themselves the lands they had thus overrun.

While the Jews were in captivity, much of the land of Israel was seized on, and occupied by the Philistines, and other nations that bordered on Judea.

- Adam Clarke's Commentary on the Bible