A confession is a request for pardon, because whoever asks pardon confesses a wrongdoing. So it is shown that penitence is acceptable to God, because he desires this, rather than the death of a sinner. A debt, in scripture, is an image of a wrongdoing, because wrongdoing always owes a debt to judgment and is avenged by it; neither does it avoid the justice of restitution unless restitution be given, just as the master remitted the debt of his servant. For the lesson of the entire parable points this out. 

How rash it is to waste prayer by continuing in anger.