If a person has grasped the meaning of God's grace in his heart, he will do justice. If he doesn't live justly, then he may say with his lips that he is grateful for God's grace, but in his heart he is far from him. If he doesn't care about the poor, it reveals that at best he doesn't understand the grace he has experienced, and at worst he has not really encountered the saving mercy of God. Grace should make you just.
Generous Justice: How God's Grace Makes Us Just (ed. Hachette UK, 2010) - ISBN: 9781444702828