John 19:31
The Jews therefore, because it was the preparation, that the bodies should not remain upon the cross on the sabbath day, ( for that sabbath day was an high day,) besought Pilate that their legs might be broken, and that they might be taken away.
The Jewish leaders asked Pilate to have the legs of the crucifixion victims broken to hasten their deaths and to have their bodies removed before sunset, because the Sabbath was approaching and that Sabbath was a high day. Their stated concern was that bodies left on the cross would defile the Sabbath and violate its sanctity. That concern for the Sabbath served as a pretext, for they really feared that people would keep thinking about the events surrounding the crucifixion and that further attention to those events would bring consequences upon themselves. The priests and rulers did not want the body left on the cross during the Sabbath because the death was already drawing attention to the life and mission, and they feared the effect of a dead Christ more than that of a living one.
The two men crucified with Jesus had their legs broken to hasten their deaths, but Jesus was already dead so his legs were not broken. His unbroken bones fulfilled prophecy and corresponded to the Passover requirement that the sacrifice remain whole. The verse belongs to the account of the death and the preparations for burial, when Joseph asked Pilate for the body after Jesus was already dead and Pilate verified the death by questioning the centurion who commanded the soldiers at the cross, who confirmed it.