God would not rub so hard

(Thomas Brooks, "The Privy Key of Heaven" 1665)

"I will turn My hand against you and will burn away
your dross completely; I will remove all your impurities."
     Isaiah 1:25

Afflictions cleanse and purge away the dross, the filth,
and the scum of the Christian.

All the harm the fire did to the three children, or rather
the three champions--was to burn off their cords. Our
lusts are cords of vanity, but the fire of affliction shall
burn them up. Sharp afflictions are a fire--to purge out
our dross, and to make our graces shine; they are a
potion--to carry away ill humours; they are cold frosts
--to destroy the vermin; they are a tempestuous sea--
to purge the wine from its dregs; they are a sharp
corrosive--to eat out the dead flesh.

Afflictions are compared to washing--which takes away
the filth of the soul, as water does the filth of the body.
God would not rub so hard
, were it not to fetch out
the dirt and spots that are in His people's hearts.