"Sin is spiritual filthiness.

Sin . . .
  the conscience,
  corrupts the imagination,
  depraves the heart,
  perverts the will, 
  pollutes the mind,
  sets the tongue on fire by hell,
  stains the life, and
  renders the man totally and eternally unfit for Heaven!

It is God's work to cleanse a sinner. No one else can.

The sinner cannot cleanse himself--he is without the means, the will, or
the power! But God in mercy does, and He does it . . .

His Son, atoning;
by His Spirit, renewing;
by His Providence, working;
and by His Truth, purifying."

James Smith (1802—1862) , "Daily Bible Readings for the Lord's Household"