Covenant: Legal or Filial?

Is the covenant between God and His people more or less strictly legal, a contractual relationship of Lord to servant? Or does it describe an ordered relationship of filial love, a relationship of Father and Son? The parable of the “prodigal son” sheds some light. Brendan Byrne points out that the older brother sees himself as a servant in the house, working like a slave, rather than as a son: “He thinks that such work should have earned a decent reward; he is in a ‘contract’ relationship with his father. He disowns his brother as brother, referring to him simply as ‘your son’ (his father, too, he bluntly addresses as ‘you’). What he resents particularly is that his brother has ‘devoured’ the family property, lessening the amount that will eventually fall to himself.” Of course, the older brother of the parable represents the scribes and Pharisees who have been complaining about Jesus’ generosity to publicans and sinners. They are apparently the ones who are treating the covenant relation of Yahweh and Israel as legal-contractual, master-slave. Just as clearly, that is not how the father of the parable nor how Jesus conceives of the relationship. For Jesus, the covenant relation of Yahweh and Israel is filial.
On a somewhat different, but related note, Byrne points out that the parable raises questions about the overly tolerant nature of God, and poses these questions to a reader: “Can you cope with a God imaged by the father in this parable? Do you find in yourself some stirrings of the (understandable) resistance of the older brother? Can you be part of a family whose hospitality is so extravagant, so uncalculating, so indulgent of human failing as this?”