Matthew 21:24

And Jesus answered and said unto them, I also will ask you one question, which if ye tell me, I likewise will tell you by what authority I do these things. The baptism of John, whence was it? from heaven or from men? And they reasoned with themselves, saying, If we shall say, From heaven, he will say unto us, Why then did ye not believe him?

The proposition Christ made was fair and sincere. If those complainers would answer a simple question he had for them, Christ agreed to answer theirs. Furthermore, Jesus well knew that they were able to answer the simple question he asked.

Then came the question regarding the baptism of John. It was devastating for those hypocrites, because they, contrary to popular belief, had rejected John as a true prophet and had refused to acknowledge his witness of Christ as being the true "Lamb of God." They were quick to see that not Christ but they themselves were trapped by the question; and, after a conference, they elected to lie about it pretending not to know the answer.

Of course, Christ rejected their question, not only because they knew the answer already, but because they were completely prejudiced against the truth. It would have been casting pearls before swine if he had answered them. Yet even when confronted by their hatred and falsehood, the Lord uttered a beautiful parable setting their conduct in such a frame of reference as to show, even at that late hour, his hope of recovering some of them from their blindness and sins.