It was the preparation; not to the passover, (for that was celebrated the night before), but to the weekly sabbath; and they judged according to the law, Deuteronomy 21:23, that the land would be defiled if the persons executed were not buried that day, but their bodies should remain on the tree all night, especially on the sabbath, which began immediately after sunset. And this sabbath was a more than ordinary sabbath, for it was not only the weekly sabbath, but also their second day of unleavened bread; which, and the last day, were both very solemn days, as may be seen, Leviticus 23:1-44. This makes them come and beseech Pilate that the bodies might be taken down, and in order to it, that their legs might be broken, lest any life remaining in them they should revive and escape.
Related Commentaries of John 19:31
John 19:31
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.