Jeremiah 23:37 - Ellicott's Commentary On The Whole Bible

Thus shalt thou say to the prophet... — The verse repeats Jeremiah 23:35, with the one difference that men are to use this, the simpler form of language, when they come to the prophet, as well as when they are speaking one to another. The affectation of big words was equally out of place in either case. In modern phraseology, the whole passage is a protest against the hypocrisy which shows itself in cant — i.e., in the use of solemn words that have become hollow and unmeaning.