John Gill Commentary Jeremiah 9:12

"Who is the wise man, that may understand this? and [who is] he to whom the mouth of Jehovah hath spoken, that he may declare it? wherefore is the land perished and burned up like a wilderness, so that none passeth through?" — Jeremiah 9:12 (ASV)

Who is the wise man that may understand this? &c.] Not the calamity, but the cause of it; a man of wisdom would inquire into it, find it out, and understand it; but the intimation is, that there was not a wise man among them, at least very few; there were scarce any that took any notice of these things, or were concerned about them:

and who is he to whom the mouth of the Lord has spoken; and foretold this desolation and destruction; meaning a prophet:

that he may declare it; as from the Lord, namely, what follows:

for what the land perishes, and is burnt like a wilderness, that none passes through? that is, what were the sins of the inhabitants of the land, which brought such distress upon it, and for which it became such a ruinous heap, and like the heath in the wilderness, so that it had no inhabitant, nor even a passenger: they must be some very great and abominable iniquities that were the cause of all this.