John Gill Commentary Jeremiah 27:9

"But as for you, hearken ye not to your prophets, nor to your diviners, nor to your dreams, nor to your soothsayers, nor to your sorcerers, that speak unto you, saying, Ye shall not serve the king of Babylon:" — Jeremiah 27:9 (ASV)

These words are not directed to the Jews, but are a continuation of what the messengers of the nations should say to their masters from the God of Israel, by the mouth of his prophet. For they had their prophets as well as the Jews, such as the prophets of Baal, and others.

Therefore hearken not you to your prophets (false prophets, as the Targum notes), nor to your diviners (or soothsayers, such an one as was Balaam), nor to your dreamers (or "dreams" such as they had themselves, and laid great stress upon, or to those who pretended to interpret them to them).

Nor to your enchanters (or stargazers, astrologers, who pretended by the position of the stars to foretell what would come to pass), nor to your sorcerers (or wizards, or necromancers, who, by unlawful methods, pretended to acquire knowledge of future things).

Which speak unto you, saying, you shall not serve the king of Babylon; meaning, either that they ought not to become tributary to him, or they should not be brought into subjection by him, and so were stirred up to oppose him, and not submit to him.