III. Dioscorus, who in his madness has attacked even the bishop of Rome, has shown himself the instrument of Satan.
It is not to be wondered, then, that they who have accepted a delusion as to our nature in the true God agree with their father on these points also, maintaining that what was seen, heard, and in fact, by the witness of the gospel, touched and handled in the only Son of God, belonged not to that to which it was proved to belong, but to an essence co-eternal and consubstantial with the Father: as if the nature of the Godhead could have been pierced on the Cross, as if the Unchangeable could grow from infancy to manhood, or the eternal Wisdom could progress in wisdom, or God, who is a Spirit, could thereafter be filled with the Spirit.
In this, too, their sheer madness betrayed its origin, because, as far as it could, it attempted to injure everybody. For he, who afflicted you with his persecutions, led others wrong by driving them to consent to his wickedness. Yea, even us too, although he had wounded us in each one of the brethren (for they are our members), even us he did not exempt from special vexation in attempting to inflict an injury upon his Head with strange and unheard of and incredible effrontery. But would that he had recovered his senses even after all these enormities, and had not saddened us by his death and eternal damnation.
There was no measure of wickedness that he did not reach: it was not enough for him that, sparing neither living nor dead, and repudiating truth and allying himself with falsehood, he imbrued his hands, that had been already long polluted, in the blood of a guiltless, Catholic priest. And since it is written: “he that hates his brother is a murderer:” he has actually carried out what he was said already to have done in hate, as if he had never heard of this nor of that which the Lord says, “learn of Me; for I am meek and lowly in heart, and you shall find rest unto your souls: for My yoke is easy and My burden is light.”
A worthy preacher of the devil's errors has been found in this Egyptian plunderer, who, like the cruellest tyrant the Church has had, forced his villainous blasphemies on the reverend brethren through the violence of riotous mobs and the blood-stained hands of soldiers. And when our Redeemer's voice assures us that the author of murder and of lying is one and the same, He has carried out both equally: as if these things were written not to be avoided but to be perpetrated: and thus does he apply to the completion of his destruction the salutary warnings of the Son of God, and turns a deaf ear to what the same Lord has said, “I speak that which I have seen with My Father; and you do that which you have seen with your father.”
Source: Letters (New Advent)