Saint Augustine 
To Consentius Against Lying 

From the Retractations, Book II, Chapter 60: Then also I wrote a Book against Lying, the occasion of which work was this. In order to discover the Priscillianist heretics, who think it right to conceal their heresy not only by denial and lies, but even by perjury, it seemed to certain Catholics that they ought to pretended themselves Priscillianists, in order that they might penetrate their lurking places. In prohibition of which thing, I composed this book. It begins: Multa mihi legenda misisti.