Throughout the centuries, when this text is taught in church or religious education programs, the almost exclusive focus has been on how the father freely receives his penitent younger son. The first time I heard the parable, I imagined Jesus’s original listeners’ eyes welling with tears as they heard how God will always love and welcome them, no matter what they’ve done. We sentimentalize this parable if we do that. The targets of this story are not ‘wayward sinners’ but religious people who do everything the Bible requires. Jesus is pleading not so much with immoral outsiders as with moral insiders. He wants to show them their blindness, narrowness, and self-righteousness, and how these things are destroying both their own souls and the lives of the people around them. It is a mistake, then, to think that Jesus tells this story primarily to assure younger brothers of his unconditional love.
No, the original listeners were not melted into tears by this story but rather they were thunder-struck, offended, and infuriated. Jesus’s purpose is not to warm our hearts but to shatter our categories. Through this parable Jesus challenges what nearly everyone has ever thought about God, sin, and salvation. His story reveals the destructive self-centeredness of the younger brother, but it also condemns the elder brother’s moralistic life in the strongest terms. Jesus is saying that both the irreligious and the religious are spiritually lost, both life-paths are dead ends, and that every thought the human race has had about how to connect to God has been wrong.
– Tim Keller