A.T. Robertson Commentary Matthew 27:18

"For he knew that for envy they had delivered him up." — Matthew 27:18 (ASV)

For envy (δια φθονον). Pilate was dense about many things, but he knew that the Jewish leaders were jealous of the power of Jesus with the people. He may have heard of the events of the Triumphal Entry and the Temple Teaching. The envy, of course, came primarily from the leaders.