The parable of the 'prodigal son' (Luke 15:11-32) is now overshadowed by the grumpy 'loyal son'.  Of the two lads, the younger chose to waste his father's inheritance while the older son remained working on the farm.  But his reaction to his younger brother's return was anger and contempt.  He was intensely jealous of the extravagance of the love which was showered on the one who did not deserve it (1 John 3:1).  

Arguing with his father, the older son exposed his attitude of resentful and grudging compliance when he protested that he never had any celebration with his friends and a reward for his dutiful service.  The wise father responded that the whole estate belonged to the whole family; but for one who disowned his family and then returned, a celebration was in order.  It was a public gift to show that he was fully restored to the family. Although the older son was invited to join in, the story does not tell his final reaction.  Jesus intended that ‘hanging' ending would provoke the dutiful religious people to wonder if they were really in relationship with God – as Jesus welcomed the corrupt tax collectors and immoral people (Luke 15:1-2).  

The parable was all about God's grace to repentant sinners.  The older son represented religious Israel who did all the right things but had the wrong motives.  They could not see any way to God's favour apart from their slavery to the law, and they resented the way that Jesus freely welcomed sinners.  As the church became established, that mind-set continued to obstruct faith in Jesus; it had to be demolished by the apostles’ teaching (Galatians 3:1-6).

Since then, the church has tended to be legalistic in different ways, crushing the life out of the gospel and seeking to control believers by rules which Jesus would not approve (Luke 11:46).  Today, many people will profess belief in God (James 2:19).  However, it is important to grasp that salvation is God's free gift and is not granted on the basis of good works - it is by God's grace alone (Ephesians 2:8-9).  Those who cannot accept this are like the older son, who could not see over the horizon of his own merit.  Those who are born again by the Spirit of God are like the younger son, who admit their sins and seek forgiveness as a normal part of their discipleship.  But remember that it is not our job to judge others, or to assess their suitability for God's favour. “The Lord does not look at the things people look at. People look at the outward appearance, but the Lord looks at the heart.” (1 Samuel 16:7). "God's solid foundation stands firm, sealed with this inscription: ‘The Lord knows those who are his,’ and, ‘Everyone who confesses the name of the Lord must turn away from wickedness.’" (2 Timothy 2:19).