Malachi 2:7

For neither may we address ourselves to almighty God, but only by Christ. In the same manner, therefore, let the laity make known all their desires to the bishop by the deacon, and accordingly let them act as he shall direct them. For there was no holy thing offered or done in the temple formerly without the priest. "For the priest's lips shall keep knowledge, and they shall seek the law at his mouth," as the prophet somewhere says, "for he is the messenger of the Lord God almighty."

See the apostle's wisdom; to obviate the objection that he was prompted by vainglory to applaud his own doctrine, he includes himself also in his anathema. And as they betook themselves to authority, that of James and John, he mentions angels also, saying, "Tell me not of James and John; if one of the most exalted angels of heaven corrupt the gospel, let him be anathema." The phrase "of heaven" is purposely added, because priests are also called angels. "For the priest's lips should keep knowledge, and they should seek the law at his mouth, for he is the messenger angel of the Lord of the hosts."

For this reason we ought to fear lest the harsh rebuke of the prophet be directed toward us: "Dumb dogs are not able to bark." By the barking of dogs and the shepherd's staff the fury of wolves is to be warded off. Now it …

For in sacred language teachers are sometimes called prophets, in that, by pointing out how fleeting are present things, they make manifest the things that are to come. And such the divine discourse convinces of seeing false things, because, while fearing to reprove faults, they vainly flatter evil doers by promising security: neither do they at all discover the iniquity of sinners, since they refrain their voice from chiding. For the language of reproof is the key of discovery, because by chiding it discloses the fault of which even he who has committed it is often himself unaware. Hence Paul says, "That he may be able by sound doctrine even to convince the gainsayers." Hence through Malachi it is said, "The priest's lips keep knowledge, and they shall seek the law at his mouth." Hence through Isaiah the Lord admonishes, saying, "Cry aloud, spare not, lift up thy voice like a trumpet." For it is true that whosoever enters on the priesthood undertakes the office of a herald, so as to walk, himself crying aloud, before the coming of the judge who follows terribly.

Here is a memorial of the fidelity and zeal of many of their predecessors in the priest's office, which are mentioned as an aggravation of their sin in degenerating from such honourable ancestors and deserting such illustrious examples, and as a justification of God in withdrawing from them those tokens of his presence which he had granted to those that kept close to him.