Matthew Poole and continuators on Jeremiah 6:28

28 They are all grievous revolters, walking with slanders: they are brass and iron; they are all corrupters.

Obstinate, and refractory, Isa. 31.6. chap. 5.3, 23.

Being their main business to detract from thee, and the other Prophets, chap. 18.18. and 20.10. a sin expresly forbidden, Lev. 19.16.

This to the end of the Chapter is all metaphorical, either they are impudent, as brass doth sometimes signifie, or they are obstinate, and in[illegible: 1 letter]lexible, as Iron notes; see both Isa. 48.4. or it signifies their corrupt estate, they are not pure Metal, as Silver or Gold, but base, and mean, as Brass and Iron mixed together, Ezek. 22.18.

This relates to their manners; they propagate their corruption, Isa. 1.4. they strengthen one another in wickedness.

Marginal references: chap. 9.4.