John 19:31

The "day of preparation" was Friday, the day before the Sabbath (Saturday, cf. John 19:14; Mark 15:42). The Jews considered sundown the beginning of a new day. In this case the new day was a Sabbath. This Sabbath was an extra special day because it fell during Passover week. The Jews wanted to get the bodies down off their crosses so they would not defile the land. The Mosaic Law instructed the Jews to allow no one to remain hanging on a gibbet overnight because this would defile the land. Such a person was under God’s curse (cf. Deuteronomy 21:22-23; Joshua 8:29). To allow someone to remain overnight on a Passover Sabbath would be especially inappropriate.

Normally the Romans left victims of crucifixion hanging until they died, which sometimes took several days. Then they would leave their corpses on their crosses until the birds had picked the flesh off them. If they had to hasten their deaths for some reason, they would smash their legs with an iron mallet. This prevented the victims from using their legs to push themselves up to keep their chest cavities open allowing them to breathe. Death by asphyxiation, loss of blood, and shock would follow soon. [Note: Carson, The Gospel . . ., p. 622.] Archaeologists have found the remains of a victim of crucifixion with his legs smashed in Israel. [Note: N. Haas, "Anthropological Observations on the Skeletal Remains from Giv’at ha-Mivtar," Israel Exploration Journal 20 (1970):38-59.]

"Thus the ’breaking of the bones’ was a sort of increase of punishment, by way of compensation for its shortening by the final stroke that followed." [Note: Edersheim, 2:613.]