Barabas is a fictional character who appears at the centre of Christopher Marlowe's play "The Jew of Malta".
In the play Barabas is a jew who fights against the warring Turks which siege Malta just after he switches to the Christians side.
Barabas represents a liar and a killer (sinner) which should be punished with death - given the chorus meaning.
Barabas could be said to portray very well the mindset of those who are suppressed or looked down upon, or whose lives are dominated by money or personal impulse. Perhaps that is why the Prologue of the play introduces it as "The Tragedy of a Jew".