The ancient pagans put great stock in saying elaborate prayers, and often held to magic formulas wherein invoking their deity's name a certain number of times (or speaking its many names in a particular order) would guarantee success.
In this parable (Luke 18:1-8), the unjust judge rules favorably for the persevering widow (to rid himself of the aggravation). How much more favorably will the God of Justice look upon those who persist in prayer.
