When the Lord chastises a people, the chastisement begins with the priest, for he is the cause of the sins of the people, either by his bad example, or by his negligence in attending to their sanctification. Hence the Lord says, The time is that judgment should begin at the house of God (1 Peter iv, 17) In the slaughter described by Ezechiel, God wished the priests to be the first victims of his vengeance: Begin ye at my sanctuary. (Ezech. ix, 6) That is, says Origen, "with the priests." A most severe judgment, says the Wise Man, for them that bear rule. (Wisdom vi, 6). And unto whom, says Jesus Christ, much is given, of him much shall be required. (Luke xii, 48).
St. Alphonsus Liguori, The Dignity and Duties of the Priest, Chapter IV, Chastisement of the Sinful Priest