In the story of the Prodigal Son in today's Gospel, the young man squandered everything and did so in the most debaucherous ways, yet his father still celebrated his return and restored his position in the family. Many people misunderstand the word "prodigal," thinking that it means lost, based on its use in this famous parable. However, it means "extravagant" or "lavish" usually in a reckless manner. While that certainly pertains to the son in this story, I also believe that it applies to his father's mercy towards him--and thus God's mercy towards us.
Yet so many Christians act like the other brother in the parable, angry at the forgiveness given to others who so clearly did not deserve it. Jesus has us spend some time with that brother just as He spends time with the envious day-workers in another parable of His. Jesus wants those who would deny forgiveness to understand that doing so is against God's nature and His law. God's love is infinite, and we should not be jealous of the pieces of it which others receive.