Surprise! The story of the prodigal son isn’t over yet. Remember that the son that squandered his share of the inheritance has an older brother? Do you remember what got Jesus started with telling these stories in the first place?
While the father has gotten his household to celebrate the return of his son, his firstborn comes in from the field and wonders what is going on. When he finds out it is about his younger brother, he gets mad and refuses to go in to celebrate. His father comes out to ask him to come in, but he accuses him of playing favorites, because he never got even a small feast for his friends despite faithfully serving his father for so long. So the father reminds him that he is going to inherit everything his father will have, and has enjoyed being with his father the entire time. Yet, that doesn’t negate the suitability of celebrating his brother’s return.
Ever see a new believer join the church and start shaking things up because they are so on fire for the Lord? Notice how it makes the old sticks in the mud uncomfortable? That’s more or less what was happening with the Pharisees and the older brother in the story. God was doing amazing things in people’s lives, and the traditionalists were unhappy about it because it wasn’t according to their way of doing things. But God isn’t constrained by how we’ve done things before, or even how He has done things before. His only constraints are His own character, and He will have mercy on whom He has mercy.
Remind us that we are sinners saved by grace, and no better than anyone else.