At the annual celebration of the Passover in Jerusalem (see note on Matthew 26:19), the Roman governor released on Jewish prisoner who was selected by the people. This was a gesture of goodwill to the Jews, who resented the Roman occupation of their country.
Rather than choosing Jesus for release, the crowd selected instead a murderer and insurrectionist named Barabbas. The Jewish religious leaders had worked the crowd behind the scenes to influence their choice (Mark 15:11).
MARK 15:6 – Now at that feast he [Pilate] released unto them one prisoner, whomsoever they desired.