5 Consider a similitude or comparison drawn from a contrary case (as of that unjust judge), which is an encouragement to us to prayer. “There was,” says the Lord, “in a city a certain judge, which feared not God, neither regarded man.” A certain widow importuned him daily, and said, “Avenge me.” He would not for a long time; but she ceased not to petition, and he did through her importunity what he would not of his own good will. For thus by a contrary case has He recommended us to pray.
Source: Sermons on Selected Lessons of the New Testament (New Advent)