Without a doubt, the parable of the prodigal son ranks among the most memorable and powerful stories that Jesus ever told. In it, we learn much about the character of God and the attitude that we are to have toward other forgiven sinners. Yet, as it is part of a set of parables that Jesus tells in response to a particular situation, we must first look briefly at the context if we are to understand it properly.
Our Lord was motivated to tell this parable after He heard some Pharisees and scribes grumbling about His eating with "sinners" (Luke 15:1–2). Remember that the religious leaders of Jesus' day, while they might have acknowledged that they sinned from time to time, did not view themselves as "sinners." That was a category that applied to those who were "worse" than they were—tax collectors, prostitutes, and others. These sinners, thought the Pharisees and scribes, were beyond the reach of God's grace. They were so corrupt that no truly holy person could eat with them and escape defilement.
Of course, passages such as Matthew 23 indicate that the views of the Pharisees about their own holiness were sorely mistaken. But the fact that these individuals were also sinners is not the point in the parable of the prodigal son. Instead, their understanding that the most notorious sinners could never find a restored relationship with God comes under criticism. The parables of the lost sheep and the lost coin, which precede the parable of the prodigal son, point us toward seeing that heaven takes great joy in extending grace to the worst of sinners. When that which was lost has been found, a celebration follows, and this is particularly true when lost men and women, who as divine image-bearers are the most valuable beings God has created, receive the Lord's grace and return to Him (Luke 15:3–10).
The Pharisees and the scribes are represented in the parable of the prodigal son by the older brother, who is resentful at his father's embrace of his sinful sibling (vv. 28–29). How could his father welcome back this son who squandered his father's gifts in riotous living and great sin? But such a viewpoint shows the failure of the older boy to understand God's attitude toward fallen people, and thus it shows how wrong the Pharisees and scribes were to cast aspersions on Jesus' dining with sinners. The Lord rejoices whenever a sinner turns from His wicked ways and returns to Him. Let us also rejoice.
If we are not careful, we may adopt a holier-than-thou attitude just like the one that the Prodigal Son's brother possessed. We dare not close the doors of our churches to the most notorious sinners. If they have repented and turned to Christ, we must likewise embrace them. If we do not, then we likely have not understood our own unworthiness and the lavish gift of grace God has given to us.