Fetch out the dirt and spots

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

"I will turn my hand against you; I will thoroughly
 purge away your dross and remove all your
 impurities." Isaiah 1:25

By severe providences and by fiery trials, God designs
the growth of His people in grace. Usually the graces of
the saints thrive best—when they are under a smarting
rod. Grace usually is in the greatest flourish—when the
saints are under the greatest trials. The trimming of the
candle—makes it burn the brighter. God bruises His
spices—to make them send forth the sweeter fragrance.
Fiery trials are like the brush, which, though it is sharp
and scratching—it makes the cloth more pure and clean.
God would not rub so hard, were it not to fetch out the
dirt and spots
which are in His people.

Stars shine brightest in the darkest nights; and so do
the graces of the saints shine brightest in the darkest
nights of affliction and tribulation. God will sometimes
more carry on the growth of grace by a cross than by
a mercy. Yes, the Lord will, sooner or later, more or
less—turn all fiery trials into blessings for the helping
on the growth of grace in His people's souls. Though
fiery trials are
grievous—yet they shall make us more
gracious. Though for the present they appear to harm
and damage us; yet in the outcome we shall find that
God will turn them into the spiritual and eternal
advantage of our precious souls.

Thrice happy will afflicted Christians be, if under all
their crosses and losses they grow into a more deep
acquaintance with God and His holiness; with the
vanity, mutability, impotency, and uncertainty of
the world; and with the deceitfulness, vileness,
baseness, and wretchedness of their own hearts!

If under fiery dispensations, we grow . . .
  more holy than ever,
  more humble than ever,
  more heavenly than ever,
  more meek and lowly than ever,
  more tender and compassionate than ever,
  more faithful and fruitful than ever,
  more patient and contented than ever,
then we may be confident that the grand design
of God in bringing all those fiery trials upon us, was
for His glory, and our own spiritual and eternal good.

"God disciplines us for our good, that we may
 share in His holiness." Hebrews 12:10