What does Luke 20:5 mean?
A group of Jewish leaders has challenged Jesus, asking who gave Him the authority to drive out merchants and money changers from the Temple Mount. These were businesses from which Jesus' accusers probably made money. If Jesus says He received His authority from heaven, the Old Testament lawyers can accuse Him of blasphemy. Jesus goes a different direction: He challenges them to declare whether they believe John the Baptist, the witness who claimed Jesus' authority came from heaven (Luke 19:45—20:4).This puts the group in a bind. They would love to be able to say that John the Baptist was a heretic. But it is the week before Passover. Jerusalem is filled with hundreds of thousands of Jews, many of whom had once flocked to John and took his baptism of repentance. The love of John is so strong that years later, Paul will meet twelve men in Ephesus who still follow John's message. As John intended, that message prepared them to accept Jesus as the Messiah (Acts 19:1–7).
Despite how much Jesus' accusers would like to disavow John, they're afraid. They're surrounded by people who are listening to Jesus teach—the same Jesus whom John claimed is the Lamb of God, the Son of God (John 1:29–34). The leaders want Jesus arrested, but they want to not be stoned by the people more (Luke 20:6). So, they will take the least honest and safest approach: to lie about their convictions to avoid trouble (Luke 20:7).