The silkworm

(Spurgeon, "The Deep-seated Character of Sin")

Nothing is more pleasing to human nature
than the attempt to do something by which
it may merit salvation at the hand of God.

Man is much like a silkworm, he is
a spinner and weaver by nature.

A robe of righteousness is wrought out for
him, but he will not have it. He will spin
for himself, and like the silkworm, he spins,
and spins, and he only spins himself a shroud.

All the righteousness that a sinner can make
will only be a shroud in which to wrap up his
soul, his destroyed soul, for God will cast
him away who relies upon his works.