This reminds us of our need to be persistent in prayer as well as persistent in seeking true justice and peace in the world.
But our Lord adds to the end of this story the following question:
But when the Son of Man comes, will he find faith on earth?
This reminds us to be persistent in our faith.
It also reminds us that none of this persistence is easy for human beings.
We need to pray always for the grace of persistence in faith, persistence in justice, and persistence in prayer itself.