Over-familiarity of a text can lead to scribal corruptions, as has been shown to have happened in the copying of remembered, preached versions of Scripture into biblical texts. This process, however, also goes the other way-the scribe's memorised version of the Bible can corrupt the copying of a non-scriptural text when the Bible is cited. This phenomenon is notable in the corpus of Leo the Great, the first pope after the completion of the Vulgate to leave us a substantial body of text. On many occasions, the variations for Leo's scriptural quotations have multiple attestations in the manuscript tradition. Leo's quotations are usually Vulgate, but sometimes his quotations shift from a ‘precise' reading. For example, Leo quotes Matthew as being from Isaiah, and several scribes have ‘corrected' Leo to match Isaiah. Elsewhere he adds words to make his prose flow more coherently; some scribes remove these interpolations. The opposite occurs when words ‘drop out' of his quotations. More interesting are the variations that are stylistically preferable according to the rules of Leo's Latin prose rhythm-a cause beyond faults of memory or multiple translations. By examining the dangers inherent in copying well-known texts, my paper will question the usefulness of the Fathers for biblical textual criticism and observe the fluidity of their biblical text, highlighting memory and style as important factors in the patristic quotations of Scripture.