The well-known parable from Luke 10:29-37:

But he, desiring to justify himself, said to Jesus, “And who is my neighbor?” Jesus replied, “A man was going down from Jerusalem to Jericho, and he fell among robbers, who stripped him and beat him and departed, leaving him half dead. Now by chance a priest was going down that road, and when he saw him he passed by on the other side. So likewise a Levite, when he came to the place and saw him, passed by on the other side. But a Samaritan, as he journeyed, came to where he was, and when he saw him, he had compassion. He went to him and bound up his wounds, pouring on oil and wine. Then he set him on his own animal and brought him to an inn and took care of him. And the next day he took out two denarii and gave them to the innkeeper, saying, ‘Take care of him, and whatever more you spend, I will repay you when I come back.’ Which of these three, do you think, proved to be a neighbor to the man who fell among the robbers?” He said, “The one who showed him mercy.” And Jesus said to him, “You go, and do likewise.”

What is the point of this story? The primary point is in answering the law-expert's question: "Who is my neighbor?" So when Jesus gets to the end, the moral imperative "Go, and do likewise" is a direct command not to be ignored by the inquisitor, or by us.

I also see what many others see in this parable: A God-loving Christianity, which is the only real kind of Christianity, is neighbor-loving Christianity, and the category of "neighbor" is not limited to those who look, think, and live like us. Our neighbors, in fact, include our enemies. So I too see the strains of kingdom-centered justice in the narrative.

But if Jesus just wanted us to know that we're supposed to care for people not like us, he could just have easily had "the man" be the hero and the Samaritan be the victim. That's in fact a more direct parallel to the flat moral imperative for Jewish lawyers to show mercy to Samaritans, or for Christians to show mercy to non-Christians. Instead, he makes the Samaritan the hero.

Why?

There is a doctrinal point in the parable, an indicative accompanying the imperative. It's why we see in the context that the inquisitor is "desiring to justify himself." It's why, I think, we get the details of the priest and the Levite passing by. These plot points are a poke in the eye of the religious establishment, of course, but casting the Samaritan as "the good guy" is a five-finger exploding heart death punch.

Making the half-breed heretic the hero evens out the playing field. It makes it abundantly clear that justification cannot come from ethnicity or religion or any other earthly badge of honor. By making the bad guy good Jesus shows how any loser is ripe for righteousness because the ground is level at the foot of the cross.

For who has loved his neighbor, who has shown mercy, more than Jesus?

For all have sinned and fall short of the glory of God.
— Romans 3:23

So then it depends not on human will or exertion, but on God, who has mercy.
— Romans 9:16