In Matthew 21 two questions are asked - one of Jesus by the religious leaders, and the other of those leaders by Jesus. The leaders' question is about "authority". They want to know the nature of the authority that is behind what Jesus is teaching and doing. Jesus asks a question about the motivations of a person's heart that lie behind one's actions.
To me this exchange exemplifies the differences between the ways of God and the ways of humanity. The same tension arises constantly in Christian churches as human legalistic views fight against the work God is doing. When it comes to actions the human concern is about the authority and correctness of them, and God's concern is for the motivations of the heart that gave rise to the actions. While the religious leaders examine the legality of things, Jesus talks about faithfulness in the heart of people who are moved to repentance.
Jesus and these religious leaders are like ships passing in the night - headed in opposite directions and talking about completely different matters. Those who talk about authority will never understand the One who came to be servant of all. In the Christian world we need less talk about who has authority and more about what is in our hearts.