They did not only prophesy falsehoods, but lies, what they knew to be false; for they pretended that God had revealed such things unto them; for admit the things they spake (as to men) but future contingencies, which might be true or false, yet it was a lie for them to pretend that God had told them any such things. The things were certainly false in themselves, being contrary to God's revelation; but setting that aside, for them to pretend God had revealed that to them which he had not revealed was a formed lie. God denieth that he ever commanded them to speak any such things, or sent them upon any such errands; they prophesied what came in their own foolish heads, and the deceits of their own hearts.
Related Commentaries of Jeremiah 14:14
Jeremiah 14:14
14 Then the LORD said unto me, The prophets prophesy lies in my name: I sent them not, neither have I commanded them, neither spake unto them: they prophesy unto you a false vision and divination, and a thing of nought, and the deceit of their heart.