These two parables in Luke 18 (The Widow & the Unjust Judge and the Pharisee and the Tax-gatherer) deal with prayer. But the underlying theme is how we achieve justification.
prayer
Prayer and rain: Does God answer prayer?
Why should I have confidence that God answers my prayers? According to James, I have confidence that my prayers will be answered because of who is answering my prayer, not because my prayer is perfect, powerful or articulate.