Luke 20:20

Luke revealed the motives of Israel’s leaders on this occasion more clearly than the other evangelists did. They watched for and made opportunities to trap Jesus. The Greek word egkathetos, translated "spy," means one hired to lie in wait. A private detective or secret agent might be closer to the ancient equivalent than a military spy. These spies feigned righteous behavior though their real purpose was to get Jesus to say something for which they might accuse Him before Pilate, the Roman governor. Later they resorted to telling Pilate that Jesus taught the people not to pay their taxes (Luke 23:2), but that was a lie.