Great Sermon! Very encouraging series. Psalm 17 is a wonderful passage. Prayer must have a solid foundation of hope that is not yet seen. It must be by faith in God's word. Not in what we see in this life.
Because in this life the wicked seem to prosper.
"You fill their womb with treasure;
they are satisfied with children, and they leave their abundance to their infants."
Hopeful prayer looks to what is to come.
"As for me, I shall behold your face in righteousness"