IV. Of all heresies Manicheism is the worst and foullest
But while he retains this ever-varying supremacy over all the heresies, yet he has built his citadel upon the madness of the Manichees, and found in them the most spacious court in which to strut and boast himself: for there he possesses not one form of misbelief only, but a general compound of all errors and ungodlinesses. For all that is idolatrous in the heathen, all that is blind in carnal Jews, all that is unlawful in the secrets of the magic art, all finally that is profane and blasphemous in all the heresies is gathered together with all manner of filth in these men as if in a cesspool. And hence it is too long a matter to describe all their ungodlinesses: for the number of the charges against them exceeds my supply of words.
It will be sufficient to indicate a few instances, that you may, from what you hear, conjecture what from modesty we omit. In the matter of their rites, however, which are as indecent morally as they are religiously, we cannot keep silence about that which the Lord has been pleased to reveal to our inquiries, lest any one should think we have trusted in this thing to vague rumours and uncertain opinions. And so with bishops and presbyters sitting beside me, and Christian nobles assembled in the same place, we ordered their elect men and women to be brought before us.
And when they had made many disclosures concerning their perverse tenets and their mode of conducting festivals, they revealed this story of utter depravity also, which I blush to describe but which has been so carefully investigated that no grounds for doubt are left for the incredulous or for cavillers. For there were present all the persons by which the unutterable crime had been perpetrated, to wit a girl at most ten years old, and two women who had nursed her and prepared her for this outrage.
There was also present the stripling who had outraged her, and the bishop, who had arranged their horrible crime. All these made one and the same confession, and a tale of such foul orgies was disclosed as our ears could scarcely bear. And lest by plainer speaking we offend chaste ears, the account of the proceedings shall suffice, in which it is most fully shown that in that sect no modesty, no sense of honour, no chastity whatever is found: for their law is falsehood, their religion the devil, their sacrifice immorality.
Source: Sermons (New Advent)