Parable of the Prodigal Son draws from Proverbs 29:3

³  A child who loves wisdom makes a parent glad, but to keep company with prostitutes is to squander one's substance. -Proverbs 29:3

From the parable of the Prodigal Son (Luke 5:11-32) has the following situation at the end: the obedient, elder son refuses to rejoice because he is feels that the younger foolish son does not deserve to be celebrated and welcomed home because of his foolishness. The elder son is practically quoting the above passage from Proverbs 29 to his father,

²⁵ "Now his elder son was in the field; and when he came and approached the house, he heard music and dancing. ²⁶He called one of the slaves and asked what was going on. ²⁷He replied, 'Your brother has come, and your father has killed the fatted calf, because he has got him back safe and sound.' ²⁸Then he became angry and refused to go in. His father came out and began to plead with him. ²⁹But he answered his father, 'Listen! For all these years I have been working like a slave for you, and I have never disobeyed your command; yet you have never given me even a young goat so that I might celebrate with my friends. ³⁰But when this son of yours came back, who has devoured your property with prostitutes, you killed the fatted calf for him!' 

Now, going a different direction with this parable. Why do we even need this last part of the parable? If the parable is solely about the grace of the father (Father) for the lost, then the point is captured with ending at verse 24. Who is meant to identify with the elder son?

¹¹ So I ask, have they stumbled so as to fall? By no means! But through their stumbling^b salvation has come to the Gentiles, so as to make Israel^c jealous. ¹²Now if their stumbling^d means riches for the world, and if their defeat means riches for Gentiles, how much more will their full inclusion mean!

¹³ Now I am speaking to you Gentiles. Inasmuch then as I am an apostle to the Gentiles, I glorify my ministry ¹⁴in order to make my own people^e jealous, and thus save some of them. ¹⁵For if their rejection is the reconciliation of the world, what will their acceptance be but life from the dead! ¹⁶If the part of the dough offered as first fruits is holy, then the whole batch is holy; and if the root is holy, then the branches also are holy.  -Romans 11:11-15