A.T. Robertson Commentary John 19:12

"Upon this Pilate sought to release him: but the Jews cried out, saying, If thou release this man, thou art not Caesar`s friend: every one that maketh himself a king speaketh against Caesar." — John 19:12 (ASV)

Sought (εζητε). Imperfect active, "kept on seeking," "made renewed efforts to release him." He was afraid to act boldly against the will of the Jews.

If thou release this man (εαν τουτον απολυσηις). Condition of third class, a direct threat to Pilate. He knew all the time that the Sanhedrin might tell Caesar on him.

Thou art not Caesar's friend (ουκ ε φιλος του καισαρος). Later to Vespasian this was an official title, here simply a daring threat to Pilate.

Speaketh against Caesar (αντιλεγε τω καισαρ). Caesar brooks no rival. Jesus had allowed himself to be acclaimed king of Israel in the Triumphal Entry (John 12:13; Luke 19:38). The Sanhedrin have caught Pilate in their toils.