Someone in the crowd said to Jesus, "Teacher, tell my brother to share the inheritance with me." He replied to him, "Friend, who appointed me as your judge and arbitrator?" Then he said to the crowd, "Take care to guard against all greed, for though one may be rich, one’s life does not consist of possessions."
Someone comes to Jesus, wanting something -- or not something, but some fleeting, insignificant little nothing. They think Jesus can get it for them, because He's a can-do sort of man.
Jesus meets them right where they are: "Friend." (Douay-Rheims: "Man.") If this fellow wants to presume some sort of special relationship with Jesus, He's more than happy to reflect that relationship right back -- and to challenge his understanding! "Why do you think I'm some circuit court judge?"
But His question isn't simply rhetorical. Jesus is, in fact, Judge and Arbitrator, and He was appointed by His Father. His challenge isn't so much to reject a false understanding of Who He Is as to complete and fulfill the fuzzy impression of Him as one possessing authority.
Then He goes on to do something remarkable: He does exactly what the man asks Him to do. The man may not have realized it, and perhaps more importantly his brother may not have realized it, but Jesus' words, "Take care to guard against all greed," are not a high-minded piety, they are a warning from the Just Judge to everyone who will come before Him for judgment.
It would do little good for Jesus to render a particular judgment in the case of the two brothers, when His authority is thought to be merely human. How would they resolve the next day's dispute, when the teacher had gone on to the next town? Instead, He points out the law by which they are to live, that day and forever. Note that, even if one brother is wholly in the wrong in the matter of the inheritance, Jesus' words do not allow the other much satisfaction, as he might have if Jesus settled the case in his favor.