Albert Barnes on Matthew 27:18

For he knew that for envy, etc. This was envy at his popularity. He drew away the people from them. This Pilate understood probably from his knowledge of the pride and ambition of the rulers, and from the fact that no danger could arise from a person that appeared like Jesus. If Pilate knew this, he was bound to release him himself. As a governor and judge, he was bound to protect the innocent, and should, in spite of all the opposition of the Jews, at once have set him at liberty. But the Scriptures could not then have been fulfilled. It was necessary, in order that an atonement should be made, that Jesus should be condemned to die. At the same time, it shows the wisdom of the overruling providence of God, that he was condemned by a man who was satisfied of his innocence, and who proclaimed before his accusers his full belief that there was no fault in him.

(t) "envy" Prov 27:4, Eccl 4:4