Expositor's Bible Commentary Commentary John 19:31

"The Jews therefore, because it was the Preparation, that the bodies should not remain on the cross upon the sabbath (for the day of that sabbath was a high [day]), asked of Pilate that their legs might be broken, and [that] they might be taken away." — John 19:31 (ASV)

Jesus died on the day preceding the Sabbath, hence, on Friday, “the day of Preparation” (cf. Mark 15:42). The day began at sunset on Thursday and ended at sunset on Friday. The meal Jesus and his disciples ate must have been on Thursday night, which would actually fall on the Passover since the Jewish day began in the evening (see comments on Jn 13:2). The removal of bodies from the cross was a concession to Jewish religious scruples. The Romans usually left the bodies of criminals on their crosses as a warning to potential offenders, much as pirates in the eighteenth century were hung in chains so that passing ships might see their fate.

The Jewish law forbade leaving hanged bodies on a gallows overnight (Joshua 8:29). The soldiers broke the legs of the living victims to hasten death. The only way a crucified man could obtain a full breath of air was to raise himself by means of his legs to ease the tension on his arms and chest muscles. If his legs were broken, he could not possibly do so; and death would follow shortly because of lack of oxygen.