A.T. Robertson Commentary Luke 23:25

"And he released him that for insurrection and murder had been cast into prison, whom they asked for; but Jesus he delivered up to their will." — Luke 23:25 (ASV)

Whom they asked for (ον ηιτουντο). Imperfect middle, for whom they had been asking for themselves. Luke repeats that Barabbas was in prison "for insurrection and murder."

To their will (τω θεληματ αυτων). This is mob law by the judge who surrenders his own power and justice to the clamour of the crowd.