English Standard Version (ESV)
Isaiah is writing to two types of people here in chapter 56. The first, previously discussed, are the forlorn and hopeless, those who have been cast aside by society. God is actively gathering them up and restoring their hope through his mercy, grace and power. The second is mentioned here -- these are the leaders who see their position as an opportunity to enrich themselves, who put their hope in their own riches and power, who have no need for a Savior because they do not see their situation as one from which they need saving.
It's a vital distinction in how we view ourselves. Are we doing pretty good, but would appreciate God's help in a few manners? Or do we recognize our true situation -- our sins have separated us from God, and without his intervention in the person of Jesus Christ, who atoned for his sins through his death on the cross, we are hopeless to approach the throne of grace.
But, because we have received grace upon grace, we can approach the throne of grace with confidence -- our sins are gone, we are free, not by our own hand but through the love and wonder of Christ.
If we rely upon ourselves, we will discover (hopefully not too late) that the situation is more grim than we had imagined.
If we rely upon God, we will discover that our hope in him is more wondrous than we might have thought.