“When Jesus returned to the Temple and began teaching, the leading priests and elders came up to him. They demanded, “By what authority are you doing all these things? Who gave you the right?”
The leading priests and elders was asking Jesus on whose authority was he performing all these miracles and teachings.
Back then when prophets was doing work of God they had to have either been chosen by God or by a leading priest or elder, so they were curious as to who gave Jesus authority to perform the miracles and teaching he was doing.
“I’ll tell you by what authority I do these things if you answer one question,” Jesus replied. “Did John’s authority to baptize come from heaven, or was it merely human?”
They talked it over among themselves. “If we say it was from heaven, he will ask us why we didn’t believe John. But if we say it was merely human, we’ll be mobbed because the people believe John was a prophet.”
Now Jesus gave them a question that has a fault in either answer they chose. For if they chose to say he was given authority from heaven then they will be questioned as to why they did not believe John when he was doing his ministry . We are told many times that the Pharisees, Sadducees, and leading presets did not get along or believe in John the Baptist so if they was to say his authority came from heaven then they would be hypocrites but if they was to say that his authority was merely human meaning that a human gave him authority to do these thing , they would be attacked and mobbed by all of his followers and from Jesus’s followers because they believed that John the Baptist was a prophet of the Lord.
So now the leading priests and elders are in a bit of a grey area because either one of their answers will end up making them look bad.
So they finally replied, “We don’t know.” And Jesus responded, “Then I won’t tell you by what authority I do these things.”
Jesus is telling them that since they cannot answer his question , then he cannot answer theirs. God gave authority to both Jesus and John to baptize, perform miracles and to preach the word of God . So by questioning Jesus they were questioning Gods authority.