The familiar Gospel from St. Luke 15 has been known to generations of English-speaking Christians as the Parable of the Prodigal Son. Some contemporary readers or hearers may think the "prodigal" is an old word for "sinful" or perhaps "ungrateful." Now certainly the younger son in the story was both sinful and ungrateful, but prodigal really means "wasteful" or "irresponsible" (especially financially). Many sermons (including some of mine) have focused on this son. And his story is dramatic. He is self-centered and selfish. He doesn't appreciate the grace of his father. He is determined to have his inheritance and do his own thing. In the process, he sinks about as low as a respectable Jew could imagine- in a pagan land, hungry, broke, dirty, in a pg pen, envying pig food. Then he remembers all the love, care and grace of his father. So he repents and heads home, trusting in the mercy of the father.
There is also another son who has stayed home and done his duty. Yet, he hasn't really appreciated the graciousness of his father. He has taken the good things for granted. And he resents his father forgiving his prodigal brother. He thinks that he has earned more consideration from the father.He is self-righteous, and in a different way, the responsible but resentful son is as self-centered and selfish as his brother. He too is a sinner who needs to repent and learn to be grateful for his father's unmerited love and grace.
This parable is really teaching us about what St. Paul writes in Ephesians 2:5, "...by grace ye are saved." Almost every human being has had times when we have been irresponsible prodigals who have wasted our heavenly Father's gifts and fallen into bad ways of living. In such circumstances, we need to come to ourselves, repent, return to our Father and depend on His loving grace.
However, sometimes we may have avoided the most obvious forms of sin. We may have tried to be good and responsible sons and daughters of God. We have done our duties. We may have been outwardly obedient in most moral and spiritual matters. Yet, we still have a natural tendency as fallen beings to trust in our merits rather than God's grace. So we too need to repent, be more thankful and learn to depend upon divine grace. No matter what sort of son or daughter of God we may be, we must realize that it is only by grace that we are saved.