The day of preparation was the Friday of Passover. According to Jewish Law (Deut 21:22-23), the dead body of a criminal who had been executed on a tree could not remain there overnight or it would be a defilement to the land. They had carefully followed this injunction in the time of Joshua (Josh 8:29, 10:26) and were still doing so around the time of Jesus, as the Jewish historian Josephus notes: “the Jews are so careful about funeral rites that even malefactors who have been sentenced to crucifixion are taken down and buried before sunset” (qt’d in Morris). This would have been even more meticulously followed since a sabbath was approaching and especially since that sabbath was a high day, which meant that it was one of the three important feast days. The Roman custom was to leave the bodies on the crosses as an advertising campaign to warn everyone of what happened to those who broke Rome’s laws, so it was necessary to get the permission of Pilate to remove the bodies. The wording of this verse hints at the possibility that if it had not been the day of preparation, they might not have bothered asking for the bodies to be taken down.

Deuteronomy 21:22-23  If a man guilty of a capital offence is put to death and his body is hung on a tree,  you must not leave his body on the tree overnight. Be sure to bury him that same day, because anyone who is hung on a tree is under God’s curse. You must not desecrate the land the LORD your God is giving you as an inheritance.

Joshua 8:29  He hung the king of Ai on a tree and left him there until evening. At sunset, Joshua ordered them to take his body from the tree and throw it down at the entrance of the city gate. And they raised a large pile of rocks over it, which remains to this day.

Joshua 10:26  Then Joshua struck and killed the kings and hung them on five trees, and they were left hanging on the trees until evening.

Those being crucified could ease the strain on their chests, thus enabling them to breathe, by pushing up with their feet, which caused them even more pain since their feet were nailed to the cross, but helped prolong their lives. When their legs were broken, their ability to push up with them was negated, causing more pressure on their chests and resulting in a much quicker death. The legs were broken by smashing them with a heavy mallet, the brutality of which contributed to a quick death by causing shock. Matthew Henry notes that “the tender mercies of the wicked are cruel” and so they are.

The Jewish leaders wanted the death process speeded up and asked that the legs of the crucified be broken. Significantly, this is the last action of the Jews recorded in John’s gospel. Morris observes that “the Jews did not want their land defiled by their dead, but they were not concerned that they were themselves defiled by their deed.”