Charles Spurgeon Commentary Jeremiah 23:16

"Thus saith Jehovah of hosts, Hearken not unto the words of the prophets that prophesy unto you: they teach you vanity; they speak a vision of their own heart, and not out of the mouth of Jehovah." — Jeremiah 23:16 (ASV)

They speak a vision of their own heart, and not out of the mouth of the LORD.

That is another of the marks of a false prophet. Such a man is a great thinker; he has thought out his theology himself, he has imagined and invented it himself: They speak a vision of their own heart, and not out of the mouth of the Lord.

Thus says the LORD of hosts, Do not listen to the words of the prophets that prophesy to you: they make you vain:

That is one mark of a false prophet: he makes you feel that you are a fine fellow, that there is something good in you: They make you vain.