Since the giving of thanks is the natural result of grace, its presence or lack of presence is an indicator of the basis by which a person lives life. A thankful person will be someone who is daily experiencing at least something of the grace of God, while someone who is bound to the law will be rigid and ungrateful. For legalists who have earned their own righteous standing, there is no one to thank – no one, of course, but themselves. So they pray to themselves and thank themselves that they are not like other people who are begging for God’s mercy. But all along, those very people who are begging for God’s mercy are receiving it and going home justified with hearts full of gratitude. And the legalist is thankful that he is not like them? Pity. If only he could be. He would be free of his pride and free of himself. He, too, could go home justified with a thankful heart.
John Fischer The Catch 