The religious gatekeepers felt profoundly threatened by Jesus because He didn't fit into any of their categories (Matthew 21:23). First, He came from Nazareth and not from Jerusalem. Second, He came from a poor family. Third, He didn't have the right rabbinic credentials. Fourth, He didn't show much regard for man-made rules. Fifth, He didn't quote an endless stream of rabbis when He gave his sermons. Sixth, He stirred up the countryside with His miracles. Seventh, He just seemed like a troublemaker. The throngs that greeted his entrance into Jerusalem proved that he was a public menace and a disturber of the peace.
It's fascinating that the Jewish leaders don't attack His teaching or His character because there was nothing to attack. So they go after His authority. That same attack has been made many times since then.
Note that our Lord answered this attacking question with a question of His own about John's baptism (Matthew 21:24-25). He thus put the religious leaders on the horns of a dilemma. They couldn't reject John without angering the people who loved him. But if they accept John, why not accept the One he came to announce? Jesus' wise response reveals that the religious leaders were cowards. They feared the crowds and they feared Jesus' popularity with the people.
Where did his authority come from? Since Jesus was sent by the Father, His authority came from God. That's why He didn't have to appeal to human tradition or to the opinions of fallible men. He spoke the truth because He is the truth (John 14:6). All authority in heaven and on earth is vested in Him (Matthew 28:18).
To this day religious types still have problems with Jesus because He doesn't fit their categories. But never mind them. As Jesus himself said, "Heaven and earth will pass away, but my words will never pass away" (Matthew 24:35).
Jesus is the Final Authority.
Taken from "Who Gave You This Authority?" by Keep Believing Ministries (used by permission).