II. The leading Jews broke their own Law, as well as failed to apprehend the new dispensation in destroying Christ
And hence, when the chief priests gathered the scribes and elders of the people together to their council, and the minds of all the priests were occupied with the purpose of doing wrong to Jesus, the teachers of the law put themselves without the law, and by their own voluntary failure in duty abolished their ancestral ceremonies. For when the Paschal feast began, those who ought to have adorned the temple, cleansed the vessels, provided the victims, and employed a holier zeal in the purifications that the law enjoined, seized with the fury of traitorous hate, give themselves up to one work, and with uniform cruelty conspire for one crime, though they were doomed to gain nothing by the punishment of innocence and the condemnation of righteousness, except the failure to apprehend the new mysteries and the violation of the old.
The chiefs, therefore, in providing against a tumult arising on a holy day, showed zeal not for the festival, but for a heinous crime; and their anxiety served not the cause of religion, but their own incrimination. For these careful pontiffs and anxious priests feared the occurrence of seditious riots on the principal feast-day, not lest the people should do wrong, but lest Christ should escape.
Source: Sermons (New Advent)