John Gill Commentary Jeremiah 29:27

"Now therefore, why hast thou not rebuked Jeremiah of Anathoth, who maketh himself a prophet to you," — Jeremiah 29:27 (ASV)

Now therefore why have you not reproved Jeremiah of
Anathoth
Not by words only, but by actions; by beating and scourging, by pillory or imprisonment, and so restraining him from prophesying to the people: which makes himself a prophet to you ?
takes upon himself such an office, though not sent of the Lord, as he would insinuate: this shows the haughtiness and insolence of the false prophets in Babylon, to assume such authority to themselves, to dictate to the high priest, as Kimchi takes him to be, or however the second priest, what he should do, and to rebuke him for not doing his office.