Miroslav Volf writes on the parable of the Prodigal Son in Luke 15 in Exclusion and Embrace (1996):

Far from completely discarding the order of the “household,” the father continues to uphold it. What the father did was to “re-order” the order! He inserted into the “must” of that order another “must” (v.32)—the “must” of embracing the returning transgressor and making him a son again, rather than locking him out of fellowship! There is a “must” of following salutary rules; but there is a “must” of receiving back the one who has broken these rules. In addition to celebrating with those who are already “in” (“friends,” v.29), one must celebrate with those who want to return.

What is so profoundly different about the “new order” of the father is that it is not built around the alternatives as defined by the older brother: either strict adherence to the rules or disorder and disintegration; either you are “in” or you are “out,” depending on whether you have or have not broken a rule. He rejected this alternative because his behavior was governed by the one fundamental “rule”: relationship has priority over all rules. Before any rule can apply, he is a father to his sons and his sons are brothers to one another. The reason for celebration is that “this son of mine” (v.24) and “this brother of yours” (v.32) has been found and has come alive again. Notice the categorical difference between how the father and how the older brother interpret the prodigal’s and constructs his brother’s departure along the axis of “bad/good” behavior: the brother has “devoured your property with prostitutes” (v.30). The father, though keenly aware of the moral import of his younger son’s behavior, employs relational categories and constructs his son’s departure along the axis of “lost/found” and “alive (to him)/dead (to him).” Relationship is prior to moral rules; moral performance may do something to the relationship, but relationship is not grounded in moral performance. Hence the will to embrace is independent of the quality of behavior, though at the same time “repentance,” “confession,” and the “consequences of one’s actions” all have their own proper place. The profound wisdom about the priority of the relationship, and not some sentimental insanity explains the father’s kind of “prodigality” to both of his sons. (164-165, emphases in the original.)