Behold, he shall come up like a lion from the swelling of Jordan against the habitation of the strong: but I will suddenly make him run away from her: and who is a chosen man, that I may appoint over her? for who is like me? and who will appoint me the time? and who is that shepherd that will stand before me? Behold, he shall come up like a lion - See the note on Jeremiah 12:5. The similitude used here is well illustrated by Dr. Blayney: "When I shall occasion a like commotion in her (Idumea) as a fierce and strong lion may be supposed to do in the sheep-folds, then I will cause him (the man of whom it is said in the preceding verse that he should not dwell in it) to run away from her as the affrighted shepherds and their flocks run from the lion."
A chosen man - Nebuchadnezzar. That is, God has chosen this man, and given him a commission against Idumea.