In his book, The Prodigal God, author and pastor Tim Keller makes the observation that Jesus gave us the parable of "The Two Lost Brothers" (or, "The Parable of the Prodigal Son") so we would see two distinct ways people rebel against God (Luke 15).
Early in the parable neither brother loves their father. The younger brother, who ended up feeding swine, rebelled by being very bad. The older brother, who never left home, rebelled by being very good. Thus the two brothers represent the two most common ways people try to make their lives and their world right without loving and enjoying God.
To use Keller's categories, some people follow the path of self-discovery. That would be the younger brother who threw off his father's authority and chased wine and women around the country. The rebellion of self-discovery loathes all constraints other than those imposed by self. Others, however, rebel by tenaciously sticking to the path of moral conformity, even at the expense of mercy (Matt. 23:23). That would be the older brother who skillfully submitted to his father's authority but boiled in anger when his brother came home.
Jesus teaches both brothers show a way of resenting and rejecting God. But the older brother, the moral conformist, is the real target of the parable, for Pharisees are present and listening closely (Luke 15:2)
The older brother believed his father should regard him more favorably because of his years of moral conformity (Lk. 15:28-30). But the older brother can not see that his moral conformity has done nothing to make him like his father. The father is genuinely glad to welcome the reckless brother home with open arms and costly gifts. The older brother will not. He does not have the compassion of his father because he does not love his father. He does not even like the way his father is. Grace violates his conscience because he deals in works. His many years of moral conformity were all for his own name so he could establish the leverage needed to get his father's inheritance. As a heartless moral conformist he outwardly looks quite different than his party-boy brother, but he is no better. He too refused to be in his father's arms (Lk. 15:28; Rom. 10:21).
The rebellion of using moral conformity to warrant our reward before the Father is the hardest for us to see because the works of the law are so attractive. This is why we can always see the rebellion of the younger brother more clearly than the older. Even our dear brother, the apostle Peter, once became fooled by the rebellion of moral conformity as grounds for a righteousness before God (Galatians 2:11-14). Thank God that Paul was given eyes to see the real rebellion in Galatia: "Did you receive the Spirit by works of the law or by hearing with faith? Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh?" (Gal. 3:2-3).
You see, because we, the Church of Jesus Christ, take holiness seriously we are a people who also take moral conformity seriously. Because we take moral conformity seriously we are easily tempted to think our moral conformity is why God loves us and not those other people. But this is a satanic lie of the highest order and it pleases our sinful nature.
God loves you on one condition and that condition is the atoning work of his crucified Son that has been imputed to you by the Spirit through the gift of faith alone. You are loved by the same measure of love the Father has for his Son, in spite of a moral conformity which is always falling short and always "accompanied by many weaknesses and imperfections" (WCF 16.6). Even that moral conformity that pleases God, those duties done sincerely and according to his commandments, they are properly attributed to the Spirit who works within you to will and to do according to his good pleasure (Philippians 2:12-13).
So this false gospel of acceptance through moral conformity has always "hung around" the Church of Jesus Christ like pilot fish feeding off the bellies of sharks. This false gospel comfortably fits in this lineage of death: some people become good through Islam, some people become good through Buddhism, some people become good through Mormonism, some people become good through Christianity. This is what many falsely believe the Christian Church is always talking about. Let us not oblige them. Let us not protect and defend the "Church of the Older Brother." Let us come out from her and reject "man's gospel" (Gal. 1:11) and hold to the true gospel of the riches of God's grace to us in Christ Jesus.
If you ever doubt the false gospel of moral conformity is the easy gospel that most men are willing to believe and so seal their destruction, consider again the younger brother in the Lord's parable. The younger brother who rebelled via the path of self-discovery came home ready to offer his moral conformity as warrant for being accepted. His life was a mess and a ruin. Using the natural mind he prepared a script that promised his father moral conformity from now on in exchange for a servant's cot and rations (Lk. 15:16-19). He did not consider mercy. It was not in his field of vision. He was ready to get in the same line his older brother had long been in. He would pledge to work off his debt and earn his keep.
But this was not the mind of his father. His father surprised him and showed him that their relationship would only have compassion and love at its cornerstone (Exod. 20:1). The father ran to him, through his arms around him, pressed his lips upon him, and dressed him as a beloved son. It is upon this gracious cornerstone - Christ crucified for sinners - that acceptable good works are built. "By them believers manifest their thankfulness" and their imperfect good works are then accepted the same way they have been - through Christ (WCF 16.2, 16.6).
These gospel truths are so important we may need to change our prayers, especially those we pray before our own sons and brothers (which is the very point of another great passage in Luke, 18:10-14).
Father, thank you for loving us when we were so worthy of your scorn. Thank you for preparing a body for your Son that we might die to the law and to sin with Him. Thank you for raising us to new life. Your are rich in pity and compassion. Forgive us our many sins and our slow faith. Grant us grace now to rise above our many corruptions. Grant us grace to keep your commandments. Help us or we will not be helped. Help us or we will not love you as we ought. We would love you from warm heart. Let it be so. Lighten our temptations today and make us willing to do your holy will. Keep us ever mindful of your grace and kingdom and our true identity as sons and daughters of the Most High God. In Jesus' name. Amen.