Jeremiah 29:8 - Ellicott's Commentary On The Whole Bible

Let not your prophets and your diviners... — The words are significant as showing that the same agencies which were counteracting the prophet’s teaching in Jerusalem were at work also in Babylon. There, too, “prophets and diviners,” whom the Lord had not sent, were prophesying of a speedy deliverance, and it was necessary to reiterate for those who would listen to the prophet’s warnings, that the exile would run its appointed course of seventy years, as Jeremiah had announced to the people of Jerusalem in Jeremiah 25:12; Jeremiah 27:22. The “dreams which ye cause to be dreamed” (an altogether exceptional phrase) indicates that the supply was created by a demand for visions of this nature.