Numerous are the sermons and commentaries I have heard on the lost sheep and the prodigal son. I have become convinced that there is a broader message that is missed because this chapter is not taken in its wider context.
Luke 14:25 states that "great multitudes" went with Jesus. This is followed by a stern discourse on discipleship with intent to thin the ranks. The Lord never appealed to the masses.
Luke led into chapter 15 with these words, "So likewise, whosoever he be of you that forsaketh not all that he hath, he cannot be my disciple. Salt is good: but if the salt have lost his savor, wherewith shall it be seasoned? It is neither fit for the land, nor yet for the dunghill: but men cast it out. He that hath ears to hear, let him hear."
Chapter 15 then starts, "Then drew near unto him all the publicans and sinners for to hear him. And the Pharisees and scribes murmured, saying, 'This man receiveth sinners, and eateth with them.'"
In that context the Lord then teaches three parables that obviously speak to both the publicans and sinners and the scribes and Pharisees. There is the lost sheep and the ninety and nine "which need no repentance." There is the lost coin. And finally and climatically there was the lost son and the elder son to whom the father said, "Thou art ever with me, and all that I have is thine."
I believe it is correct to say that the primary focus in these parables is on the lost that was found. What I believe we more often miss is the message to the scribes and Pharisees who would clearly identify with the ninety nine sheep left in the wilderness, the nine coins that were not the focus of the celebration, and the angry elder son who at the end of the story was on the outside of the feast looking in, not because he was not invited in but by his own sinful attitude.
I think the message to them was that the only path to joyful fellowship with the Father is through lostness or repentance. I think the Lord's parables were designed to help them recognize their lostness. I believe His statement about the ninety nine sheep "which need no repentance" was spoken with tongue-in-cheek and a sarcasm that was not missed by the scribes and Pharisees. When the father said, "Thou art ever with me, and all that I have is thine." it was another reality check that though they were on the inside of the religious establishment they had not cashed in their spiritual vouchers and were actually in perilous danger of missing out altogether.
We are challenged to consider that our Godly heritage and "service" to God are no substitute for repentance for sins and attitudes. They are no substitute for joyful fellowship. In fact they can become barriers to fellowship with redeemed prodigals and entering into the banquet hall to the open armed Father God.