What does Luke 20:3 mean?

After the triumphal entry, Jesus returned to the Temple Mount. There, He found the Court of the Gentiles filled with crass and corrupt business—merchants selling supplies for sacrifice and money changers exchanging Greek coins for a half-shekel—and a fee—for the temple tax. Jesus responded by driving them out. Not only were they cheating the Jews who had traveled to Jerusalem for the Passover, they were making it impossible for devout Gentiles to approach the temple and worship God (Luke 19:45–46).

A day or so later, Jesus returns to the Temple Mount to teach. Some priests, lawyers, and respected businessmen approach—just the sort of men who benefit from all those vendors. They ask Jesus by what authority He acted (Luke 20:1–2). Jesus cleverly turns the question around. He challenges the men to publicly declare whether they believe the most popular earthly witness to His authority: John the Baptist. Do they think John's teaching was purely manmade, or do they think it was divine (John 20:4).

John's baptism was a vow of repentance from sin and dedication to God. These city leaders should be able to affirm John's baptism; repentance is certainly consistent with the Mosaic law. An added incentive is that the people love John, even though he's been dead for about three years, and if they reject him, the people might stone them (Luke 20:6).

However, Jesus' enemies have several problems. First John called them a "brood of vipers" in front of a crowd (Matthew 3:7). More importantly, assigning John's teaching to God's will requires them to agree with what John said about Jesus: "Behold, the Lamb of God, who takes away the sin of the world!" (John 1:29). That would mean admitting Jesus' authority comes from God.

Instead, they claim to not know (Luke 20:5–7). Jesus has proven their insincerity; there's no reason to answer their question if they lack the conviction to answer His (Luke 20:8).

Luke's timing is vague, but Mark's Gospel provides more details (Mark 11:11–15, 20, 27).