Imagine, for a moment, that you have been invited to a banquet at Buckingham Palace. You are treated to the finest of foods, prepared by world class chefs, in the most sumptuous of surroundings, and in the presence of your most gracious host.
Toward the end of the evening you beckon over one of the royal servants attending the table. Reaching into your pocket for a twenty pound note, you quietly whisper "I wondered whether you could pass this to her majesty. A small contribution toward the evening."
That would be a great insult. It would also be a pathetically inadequate gesture in the face of overwhelming riches. Not for one moment would you think that such an act would be intelligible or appropriate.
Why then in the face of overwhelming riches of grace and wisdom in Christ, and the total sufficiency of his finished work in obtaining for us righteousness, pardon and acceptance, would we ever think that our works could be included in the basis of our being right with God?
The tragedy is that the analogy of a banquet at Buckingham Palace is an infinitely weak, pale and insignificant comparison of what God does for us in the gospel. Our boast is in the Lord, and in the Cross, to the praise of his glorious grace.