Leonard Sweet on the Parable of the Prodigals:
It has become fashionable to see the elder brother as the true “prodigal.” Coming in from his field, he heard all the ruckus and demanded: “What’s all this music and dancing?” When told his younger brother had returned and their father had rolled out the red carpet and killed a calf (notice how many times “fatted calf” crops up in the elder brother’s conversation) for a mega-party, he went ballistic.
It was hurtful for the younger son to ask his father for his inheritance ahead of time, a request that some scholars have interpreted as amounting to wishing his father’s death (“Why don’t you hurry up and die?”). What actually was the younger brother’s sin? Not “loose living,” but nonliving in relationship with his father. He valued more highly what he could get from his father than friendship with his father. In fact, the Greek text never uses the words “riotous living” or “loose living.” In the words of Herbert McCabe, “English translators have been conned by the vindictive slanders of the elder brother later in the story. Here we are just told that he spent his money… ‘without hanging on to it’ as though there were no tomorrow. His sin does not lie in sensuality and harlots. His sin is much more serious. It is in the abandonment of his father’s house.”
Quoted from Leonard Sweet, Out of the Question… Into the Mystery, p.147. Bottom line, the prodigal’s sin (both sons are the same on this) is of the most serious variety, the sin of non-relationship to their father. Seems God is big into relationship, which is the point of the story. To not live in relationship is not living… it is nonliving.