Adam Clarke on Jeremiah 23:27

Bay their dreams - Dreams were anciently reputed as a species of inspiration; see Num 12:6; 1Sam 28:6; Joe 3:1; Dan 7:1. In the Book of Genesis we find many examples; and although many mistook the workings of their own vain imaginations in sleep for revelations from God, yet he has often revealed himself in this way: but such dreams were easily distinguished from the others. They were always such as had no connection with the gratification of the flesh; they were such as contained warnings against sin, and excitements to holiness; they were always consecutive - well connected, with a proper beginning and ending; such as possessed the intellect more than the imagination. Of such dreams the Lord says, (Jer 23:28): The prophet that hath a dream, let him tell a dream - permit him to show what he has thus received from the Lord: but let him tell it as a dream, and speak my word faithfully, lest he may have been deceived.