What does Matthew 21:27 mean?
Jesus has forced those who challenged His authority into a corner by posing a question of His own (Matthew 21:23–26). In essence, He has asked whether or not John the Baptist was a true prophet. These chief priests and elders could not say yes, of course, or everyone would want to know why they did not believe John. At the same time, they realize that telling the truth—that they did not believe John—would lose the support of the many people who had a positive view of John.This reply proves these so-called leaders are willing to put partisan control over the truth. Their real priority is maintaining leverage over the people they are supposed to be leading. They would rather keep their true convictions hidden, even about something as important as whether a messenger is a prophet from God. Rather than allow their generation to challenge and disrespect them, they choose to be silent. Their integrity is being tested, and they fail miserably. Their motive for confronting Jesus was dishonest, and so is their attempt to avoid His question.
So, they now reply in the weakest, lamest way possible for men who prided themselves on their ability to debate: "We do not know." Since they did not meet His condition, Jesus tells them He won't answer their question, either. Jesus defused their attempt to catch Him speaking blasphemy by simply asking them to tell the truth about their religious convictions. They would not.
Jesus' overall message (John 5:19–24), along with the theme of the parables He is about to tell, provide an answer to the initial challenge. Christ acts under the power and authority of God.