C. F. Keil and Franz Delitzsch on Jeremiah 6:28

Jer 6:28

Jer 6:28 gives a statement as to the moral character of the people. "Revolters of revolters" is a kind of superlative, and סרי is to be derived from סרר, not from סוּר, perverse of perverse; or, as Hitz., imitating the Heb. phrase, rebels of the rebellious. Going about as slanderers, see on Lev 19:16, in order to bring others into difficulties; cf. Eze 22:9. To this is subjoined the figurative expression: brass and iron, i.e., ignoble metal as contrasted with gold and silver, cf. Eze 22:18; and to this, again, the unfigurative statement: they are all dealing corruptingly. משׁחיתים, cf. Isa 1:4; Deu 31:29. There is no sufficient reason for joining כּלּם with the preceding: brass and iron, as Hitz. and Graf do in defiance of the accents.