One commentary portrays a Christian's relationship with the law.
The elder son in this parable portrays the Pharisees and scribes. In 15:3 we see that the Lord spoke these parables to the Pharisees and scribes in the presence of the tax collectors and sinners. The religious ones must have been unhappy, but the tax collectors and typical sinners must have been filled with rejoicing. The Pharisees and scribes, however, complained that the situation portrayed in these parables was not fair.
Watchman Nee illustrates:
The story of the prodigal son gives a supreme illustration of the way to please God. The father said, "We had to be merry and rejoice" (Luke 15:32). The matter that was supremely joyful to the father's heart was not the elder brother's incessant toiling for the father, but the younger brother's willingness to let the father do everything for him. What was pleasing was not the elder brother who wanted to be the giver, but the younger brother who was willing to be the receiver. When the prodigal returned home after wasting all of his substance on riotous living, the father did not have a word of rebuke concerning the waste or a word of inquiry regarding the substance. He did not sorrow over all that was spent; he only rejoiced that the prodigal's return afforded him the opportunity to spend much more. God is so wealthy that His chief delight is to give; His treasure-stores are so full that it is painful to Him when we refuse Him an opportunity to lavish His treasures upon us. It was the father's joy that he found a willing applicant in the prodigal son for the robe, ring, shoes, and feast; it was his sorrow that he found no such application in the elder brother. It is a grief to the heart of God when we try to give things to Him, because He is so rich. It is a joy when we simply allow Him to give and give to us. It grieves Him when we try to do things for Him, because He is so able. He longs for us to simply allow Him to do everything. He wants to be the Giver and the Doer eternally. If only we saw how rich and how great He is, we would leave all the giving and doing to Him.
The prodigal son was not exempted from this either.
When the prodigal son considered his situation, he may have asked himself, "Why am I doing this? My father is very rich, so why should I perish here in famine?" This is a sinner’s repentance. However, the concept of a sinner after his repentance is to return home to work.
Therefore, the prodigal son went on to say,
"I will rise up and go to my father, and I will say to him, Father, I have sinned against heaven and before you. I am no longer worthy to be called your son; make me like one of your hired servants" (vv. 18-19).
Then he rose up and went to his father to speak according to what he had prepared.
However, the father did not want to hear what he had to say, so before the son could finish his speaking, the father interrupted him and told the servants, “Bring out quickly the best robe and put it on him, and put a ring on his hand and sandals on his feet. And bring the fattened calf; slaughter it, and let us eat and be merry” (vv. 22-23). The fattened calf signifies Christ, who is God. God in Christ has become the fattened calf for the enjoyment of the repentant and returning prodigal sons. To us, this is the jubilee.
Therefore, Luke 15:11-32 is an illustration of the jubilee proclaimed in Luke 4:18-19. The prodigal son sold his possession and himself. One day he returned to his possession and his father’s house. That was a jubilee, a liberation, and everything became pleasant and satisfying. In the father’s house there was only enjoyment with eating and drinking; there was no labor.
This corresponds to Leviticus 25:11, which says that the people were neither to sow or reap in the year of the jubilee; they should only eat and enjoy. Furthermore, they could only eat of the produce directly from the field. This means that they ate what God supplied without the need of their own labor. Similarly, the father in Luke 15 did not listen to what the son had to say about being a hired servant. Instead, the father desired to give the son the fattened calf for him to eat and enjoy. No one is unworthy; rather, all are worthy because God says, “I have accepted you.” The jubilee is the age, the time, of God’s acceptance, indicated by the father’s acceptance of the prodigal son in Luke 15.
So, the elder brother who was "positionally" in the Father's house but never "experientially" enjoyed the Father's riches. While the prodigal one, who was a sinner, did.
Why was the prodigal son spoken harshly of by his elder brother?
Just as it was portrayed by in Genesis 21 (due to Paul's allegorizing the two women in Galations), it was not the birth of Isaac that stirred up trouble; it was his growth. When Isaac was born, Hagar and her son Ishmael were not bothered very much. But after Isaac had grown up, Ishmael began to mock him (v. 9). In the biblical sense, this means that Ishmael was persecuting Isaac. God even counted Ishmael's persecution of Isaac as the beginning of the four-hundred-year persecution of His people (15:13; Acts 7:6). As Paul says in Galatians 4:29, "But as then he that was born according to flesh persecuted him that was born according to Spirit, so also it is now."
Just like the religious law-keepers people cared only for the ritual of Sabbath-keeping in John chapter 5; they had no concern for the sick man's condition. The law-keeping religion could not give life to the impotent man. When Christ enlivened this man with life, that religion persecuted Him because He did it on the Sabbath (5:16). That religion cared for the keeping of its Sabbath at the sacrifice of the impotent man's rest. But Christ cared for the man’s rest at the sacrifice of their Sabbath-keeping. This surely offended that religion.
There are many cases where religious law-keeping portrayed in the Gospels (fasting, Sabbath, eating, regulations, ordinances, and rituals etc.) exposes religious law-keeping's focus on religious regulations rather than those in real need.
Was Jesus intending to bring out the degeneration of relations over property and wealth by 'making' the elder son speak harshly of the younger one?
No. Rather, the proclamation of the jubilee in Luke 4 governs the central thought of the whole Gospel of Luke. In Ephesians 1:13-14, Paul says,
In whom you also, having heard the word of the truth, the gospel of your salvation, in Him also believing, you were sealed with the Holy Spirit of the promise, who is the pledge of our inheritance unto the redemption of the acquired possession, to the praise of His glory.
What does it mean to be saved? To be saved is to return to our inheritance, to return to God, to come back to God and enjoy Him anew as our possession (Psalm 16:5). God is our inheritance, and after we are saved, the Spirit of God is in us as the pledge, the guarantee, the proof, and the security of our inheritance (Ephesians 1:13-14).
According to spiritual significance, this story depicts a fallen man who completely lost his possession in the house of God the Father. He left his own possession and sold himself as a slave [to sin, world etc.].
Man has lost God and is without God because of the fall. Therefore, when the Bible speaks of the year of jubilee, the first thing it shows is that man must be returned to God. According to the Old Testament type, when the year of jubilee came, a person who had sold himself into slavery was returned to his own possession and to his own family to be reunited with his relatives, and at the same time he was also released from the yoke of slavery and was no longer a slave.
In the New Testament age, in Luke 4, the Lord spoke of the condition of three kinds of people.
Verse 18 says:
The Spirit of the Lord is upon Me, because He has anointed Me to announce the gospel to the poor; He has sent Me to proclaim release to the captives, and recovery of sight to the blind, to send away in release those who are oppressed.”
The three categories of people in this verse are the poor [To be without God is to be really poor], the captives, and the oppressed. On the one hand, these are three kinds of people, but on the other hand, they are three human conditions. When we lost God, we became poor, and the result of poverty was that we were captured. Then after being captured, we were oppressed. This illustrated the prodigal son's condition after he left the Father's house.