The Father in the Luke 15 story represents God, while the good son represents unregenerate good people like the Pharisees, and the bad son represents unregenerate bad people like the tax collectors.
There is a potential problem with this passage since God the Father is NOT the father of unregenerate people. At least that is what I used to believe, and in a sense I was right.
God the Father is the father of his people and his people only. However, is it possible for a person to be unregenerate and still be one of his people? The answer to this question is yes. Take the children of Israel for example who were the people of God even if most of them were unsaved. Or take children who are brought up in a Christian home. They are part of God's covenant people. This does not mean that they are saved, and this does not mean that they will be saved. But they are part of the Covenant, and are in one sense God's children. It was not until the youngest son in the Luke 15 story was saved that he truly had a relationship with his father. At the end of the story, the older "good" son who has "no need for repentance" is still a son of his father, but he does not have the kind and quality of relationship that his younger brother now has.
A person brought up in a Christian home has certain blessings that a person who is not part of the Covenant does not have. But if he is not changed by the Holy Spirit so that he repents like the Lost Son did, he will not only lose the taste of Heaven that he had in his Christian home, but he will also be spending eternity in Hell. We are left with the implied question at the end of the Lost Son story: Will the older son repent? Or to look at it another way, will the "good people" who are in no need of repentance truly repent? Being a son of God in the covenantal sense is not good enough. Being a son of God in the eternal sense is enough.
The lost sheep, lost coin, and lost son are stories about the people of God, people of the Covenant. The lost sheep, lost coin, and lost son, all represent the "bad" people with whom Jesus spent so much time. They were people of the Covenant, but they were people who lived like they were not the people of God. They were obviously bad. Jesus is criticized by "good people" for this kind of ministering. These "good" people who lived like they were in no need of repentence are seen in the story as the other sheep, other coins, and the good son. Heaven is thrilled when the lost are found, but the same is not said about the ones who live as if they are neither lost, nor in need of true repentence.
These stories do not primarily have to do with unsaved people who have never been part of God's covenant people. These stories have to do with God's covenant people, people of the church. Being part of the Covenant does not guarantee Heaven for anyone. Only the truly repentant who have been truly changed from the inside out by the Holy Spirit (the changing agent) will be spending eternity in Heaven.
