We've all been in situations where we needed rescued. Maybe your situation was dire, maybe it wasn't all that life-threatening. But either way, we know the thrill of deliverance; the joy of rescue. Psalm 40 celebrates the deliverance of God, even though the battle isn't yet won.
Jesus' authority continues to be in question as the religious leaders are hellbent on getting rid of him. They can't put him away by their own authority, so they reach for a few other options.