Their dregs and dross

(Thomas Brooks, "London's Lamentations" 1670)

 "Therefore this is what the Lord Almighty says—
 See, I will refine and test them, for what else can
 I do because of the sin of My people?" Jerem. 9:7

By severe providences and fiery trials—God designs
the mortifying and purging away of His people's sins.

"This third I will bring into the fire; I will refine them
 like silver and test them like gold." Zechariah 13:9

The best of men are but men at the best; they have
much corruption and dross in them, and they need
refining; and therefore God by fiery trials will refine
them—as silver and gold which are purified in the fire.
He will so refine them, as that they shall leave their
dregs and dross behind them. Look!
  What the fire is to the gold,
  what the file is to the iron,
  what the winnowing fan is to the wheat,
  what the soap is to the clothes—
that shall fiery trials be to the saints.

All the fiery trials which befall the saints, shall be as a
medicinal potion to purge away our soul diseases! May
our trials be so sanctified, as to issue in the burning
up of our lusts, and in the purging away of our filth!

O sirs! If God, by fiery trials, shall make you more
victorious over your strong lusts, and help you to live
more virtuous lives—you will have cause to bless Him all
your days, though He has turned you out of house and
home, and burnt up all your comforts round about you!

"He will sit as a refiner and purifier of silver; He will
purify the Levites and refine them like gold and silver."
    Malachi 3:3