John Trapp on Jeremiah 6:30

Ver. 30. Reprobate ſilver ſhall men call them] Droſs and refuſe, [non-Latin text not transcribed] unapproved. rather then pure mettal: ſilver they would ſeem to be; but their hypocriſie ſhall be made known to all men, who ſhall count them and call them reprobate, becauſe impurgabiles and inexpiabiles, uncounſellable, and incorrigible: a ſore ſign of reprobation,Hieron. Lyra. as Aquinas noteth from Heb. 6.7, 8.

For the Lord hath rejected them] As refuſe and counterfeit,Deus eſt ſapiens nummularius. ſuch as will not paſſe in payment. Hence they are to be caſt into Babylons Iron-furnace (quaſi antro Aetnao & Cyclopico adhuc decoquendi) a type of that eternal fire of hell, prepared of old for the devil and reprobates.