Behold, I am against: See 21.13.

Who use their tongues and say, ‘Says the LORD’: Who use their tongues and say is a Hebrew construction meaning “who say.” Moreover, there may be intended a play on words between the verb say (used only here in the Old Testament) and the noun “utterance” or “saying” (translated as a verb says). One commentator has expressed this as “They word it, ‘Jahweh’s word.’ ” Most translators express this sentence as “who speak their own words but say ‘This is what the LORD says.’ ”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .