4 For since it is written, “Neither shall revilers inherit the kingdom of God,” and again the Lord says in His Gospel, “Whosoever shall say to his brother, You fool; and whosoever shall say, Raca, shall be in danger of the Gehenna of fire,” how can they evade the rebuke of the Lord the avenger, who heap up such expressions, not only on their brethren, but also on the priests, to whom is granted such honour of the condescension of God, that whosoever should not obey his priest, and him that judges here for the time, was immediately to be slain?
In Deuteronomy the Lord God speaks, saying, “And the man that will do presumptuously, and will not hearken unto the priest or to the judge, whosoever he shall be in those days, that man shall die; and all the people, when they hear, shall fear, and shall do no more wickedly.” Moreover, to Samuel when he was despised by the Jews, God says; “They have not despised you, but they have despised me.” And the Lord also in the Gospel says, “He that hears you, hears me, and Him that sent me; and he that rejects you, rejects me; and he that rejects me, rejects Him that sent me.” And when he had cleansed the leprous man, he said, “Go, show yourself to the priest.” And when afterwards, in the time of His passion, He had received a buffet from a servant of the priest, and the servant said to Him, “Do you answer the high priest so?” the Lord said nothing reproachfully against the high priest, nor detracted anything from the priest's honour; but rather asserting His own innocence, and showing it, He says, “If I have spoken evil, bear witness of the evil; but if well, why do you smite me?” Also subsequently, in the Acts of the Apostles, the blessed Apostle Paul, when it was said to him, “Do you revile God's priest?” — although they had begun to be sacrilegious, and impious, and bloody, the Lord having already been crucified, and had no longer retained anything of the priestly honour and authority— yet Paul, considering the name itself, however empty, and the shadow, as it were, of the priest, said, “I knew not, brethren, that he was the high priest: for it is written, You shall not speak evil of the ruler of your, people.”
Source: The Epistles of Cyprian (New Advent)