Jesus told the parable of a persistent widow and a judge in Luke 18:1-8.
Luke 18:1-8
[1]Then Jesus told his disciples a parable to teach them that they should always pray and never become discouraged.
[2]“In a certain town there was a judge who neither feared God nor respected people.
[3]And there was a widow in that same town who kept coming to him and pleading for her rights, saying, ‘Help me against my opponent!’
[4]For a long time the judge refused to act, but at last he said to himself, ‘Even though I don’t fear God or respect people,
[5]yet because of all the trouble this widow is giving me, I will see to it that she gets her rights. If I don’t, she will keep on coming and finally wear me out!’ ”
[6]And the Lord continued, “Listen to what that corrupt judge said.
[7]Now, will God not judge in favour of his own people who cry to him day and night for help? Will he be slow to help them?
[8]I tell you, he will judge in their favour and do it quickly. But will the Son of Man find faith on earth when he comes?”