Jesus said to them, "Then neither will I tell you by what authority I act." Mark 11:33, N.E.B.
Shortly after Jesus fed a huge crowd of people with seven loaves of bread and a few small fishes, He was approached by the Pharisees who "came out and engaged him in discussion. To test him they asked him for a sign from heaven. He sighed deeply to himself and said, 'Why does this generation ask for a sign? I tell you this: no sign shall be given to this generation' " (Mark 8:11, 12, N.E.B.).
These religious leaders wanted Jesus to show them a sign to prove His authority and messiahship. Why didn't Jesus comply with their wishes? Wouldn't it have saved Him the agony of rejection by the spiritual fathers of Israel, making His mission on earth so much easier? Certainly it would have made life simpler for the disciples. Maybe that's why Jesus warned them to beware of the leaven of the Pharisees (verse 15)--to avoid their line of reasoning.
The Pharisees wanted to see firepower! After all, the Messiah was going to free the children of Israel from Roman bondage, wasn't He? Settle a few scores! Make all the surrounding nations think twice before they trespassed onto the Promised Land! But no such sign was to be given. It would have been profoundly misleading. Jesus came to reveal that God desires to love people to wholeness, not browbeat them into submission--all people, including citizens of Rome!
On another occasion, as Jesus was walking in the Temple court not long after having chased the money changers, "the chief priests, lawyers, and elders came to him and said, 'By what authority are you acting like this? Who gave you authority to act in this way?' " (chap. 11:27, 28, N.E.B.).
Jesus understood that they desired to force Him into a corner, hoping that His answer would make Him utterly vulnerable to their destructive designs on His life. Instead, Jesus countered by asking them about the authority of John the Baptist. Afraid to expose their own devious minds to the people, they declined to answer. "And Jesus said to them, 'Then neither will I tell you by what authority I act' " (verse 33, N.E.B.).
Again, for Jesus to say that God was His authority would have implied overtones of muscle power in His earthly mission. In no way would Jesus misrepresent His Father's character! Power gets people's attention, but it is a poor teacher of God's truth.