What does Luke 15:31 mean?

The prodigal son (Luke 15:11–13) has returned in humble repentance (Luke 15:21). The father has forgiven him and restored his relationship. In celebration, the father has provided a grand feast with music and dancing (Luke 15:24). The older brother is livid. Why should this shameful son receive such a celebration when he has worked so faithfully—like a slave—for his father (Luke 15:25–30)?

He doesn't see that the celebration is not for the younger brother. It is for the father. The father is filled with joy and invites others into his joy. But the father also doesn't see a functional distinction between himself and the older brother. "All that is mine is yours." That certainly includes the estate; the younger brother has already wasted his part. All the work the older brother does will come back to him upon his father's death.

As the heir, all that belongs to the father is his. This includes the reclamation of the wayward brother and the restoration of the family. It should also include the joy that overflows into a desire to invite others to celebrate.

Jesus is speaking these words to devout religious leaders, experts in the Mosaic and rabbinic laws. They are heirs of the kingdom of God. They are the ones who strive to keep a good relationship with God through work and obedience. What they miss is the loving, gracious character of God. If they could adopt God's character as their own, they would celebrate the repentance of the tax collectors and sinners with Jesus (Luke 15:1–2).