Charles Spurgeon Commentary Mark 15:6-10

"Now at the feast he used to release unto them one prisoner, whom they asked of him. And there was one called Barabbas, [lying] bound with them that had made insurrection, men who in the insurrection had committed murder. And the multitude went up and began to ask him [to do] as he was wont to do unto them. And Pilate answered them, saying, Will ye that I release unto you the King of the Jews? For he perceived that for envy the chief priests had delivered him up." — Mark 15:6-10 (ASV)

And he therefore hoped that the people, who were not moved by the same envy, would have chosen to have Jesus set free.