Children often complain about a sibling receiving more food, more desert, more attention or more affection. Sometimes they protest to their parents directly, sometimes to grandparents or friends, and while their lament sounds like it is rooted in justice, it is really an expression of their fear that they are invisible and unimportant not only their parents but to everyone. Because they have tried so hard to please their elders and superiors, they think they have earned and deserve their affection and love.
Like resentful children, the Pharisees sound like they are concerned for the Law and its careful observance, but in fact they are afraid that they are losing the empty power over the poor which they so carefully crafted. They want Jesus to recognize, honor and obey the law according to their insights, but Jesus will have none of it. Like the Pharisee in Luke's gospel who marches to the front of the synagogue comparing himself to sinners and announcing his goodness, they expect God to reward them for their fidelity to the law, only to learn that the law is not a competition but path that helps us live in God's presence as humble servants.
Are there issues in your life that cause you resentment?