The expression is that of improper form, since there are several "parables of forgiveness", and not only one. "Parable" is the expression that yields a figure of speech, i.e. to a tale that wants to convey an example, a moral, or a teaching through so-called stories, imaginary tales, say, not real. Where most commonly used is in the Bible, and specifically in the New Testament. Jesus Christ tells several "parables of forgiveness", as the of the "prodigal son", or that of the debtor that requires other debts.