From: Mark 11:27-33
 And they (Jesus and his disciples) came to Jerusalem. And as he was
walking in the temple, the chief priests and the scribes and the elders
came to him,  and they said to him, "By what authority are you doing
these things, or who gave you this authority to do them?"  Jesus
said to them, "I will ask you a question; answer me, and I will tell you
by what authority I do these things.  Was the baptism of John from
heaven or from men? Answer me."  And they argued with one another,
"If we say, 'From heaven,' he will say, 'Why then did not you not believe
him?'  But shall we say, 'From men'?"--they were afraid of the
people, for all held that John was a real prophet.  So they answered
Jesus, "We do not know." And Jesus said to them, "Neither will I tell
you by what authority I do these things."
27-33. Those who put this question to Jesus are the same people as, some
days earlier, sought to destroy him (cf. Mk 11:18). They represent the
official Judaism of the period (cf. note on Mt 2:4). Jesus had already
given proofs and signs of being the Messiah, in his miracles and
preaching; and St. John the Baptist had borne witness about who Jesus
was. This is why, before replying, our Lord asks them to recognize the
truth proclaimed by the Precursor. But they do not want to accept this
truth; nor do they want to reject it publicly, out of fear of the people.
Since they are not ready to admit their mistake, any further explanation
Jesus might offer would serve no purpose.
This episode has many parallels in everyday life: anyone who seeks to
call God to account will be confounded.
Source: "The Navarre Bible: Text and Commentaries". Biblical text
taken from the Revised Standard Version and New Vulgate. Commentaries
made by members of the Faculty of Theology of the University of
Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock,
Co. Dublin, Ireland.