Luke 18:1-8.
Jesus told a parable for people to pray always and not to faint. It was about an unjust judge and an importunate widow. This widow was not judged fairly by this unjust judge who were not afraid of God and did not respect people. The widow always came to him and asked to judge fairly again and again and again, so that the unjust judge decided that he would judge her fairly because she was so importunate.
Then Jesus said "Why don't the God judge quickly and fairly for people who are crying day and night for the fair judgement? The God will avenge them speedily."
As in the parable of "A gentile dog", it's very important key to keep pray and ask with hope and faith to the Lord.
