I. He rejoices at Pulcheria's zeal both against Nestorius and Eutyches.
That which we have always anticipated concerning your Grace's holy purposes, we have now proved fully true, viz. that, however varied may be the attacks of wicked men upon the Christian Faith, yet when you are present and prepared by the Lord for its defence, it cannot be disturbed. For God will not forsake either the mystery of His mercy or the deserts of your labours, whereby you long ago repelled the crafty foe of our holy religion from the very vitals of the Church: when the impiety of Nestorius failed to maintain his heresy because it did not escape you the handmaid and pupil of the Truth, how much poison was instilled into simple folk by the coloured falsehoods of that glib fellow.
And the sequel to that mighty struggle was that through your vigilance the things which the devil contrived by means of Eutyches, did not escape detection, and they who had chosen to themselves one side in the twofold heresy, were overthrown by the one and undivided power of the Catholic Faith. This then is your second victory over the destruction of Eutyches' error: and, if he had had any soundness of mind, that error having been once and long ago routed and put to confusion in the person of his instigators, he would easily have been able to avoid the attempt to rekindle into life the smouldering ashes, and thus only share the lot of those, whose example he had followed, most glorious Augusta.
We desire, therefore, to leap for joy and to pay due vows for your clemency's prosperity to God, who has already bestowed on you a double palm and crown through all the parts of the world, in which the Lord's Gospel is proclaimed.
Source: Letters (New Advent)