An oath was sworn by Pope Leo III at St. Peter's on December 23 of the year 800 before a synodal assembly at which Charlemagne presided; it occupies a central place among the events that culminated, only two days later, in the coronation of the Frankish king as Imperator Romanorum. The document customarily known as the text of this ‘oath’ was in 1899 edited by Karl Hampe, and in 1906 by Albert Werminghoff, who followed his predecessor ad verbum usque, as he says. The apparatus of both editions establishes the insertion of a slightly reedited oath in the Decretum of Burchard of Worms. Ivo of Chartres and, in an apologetic treatise, Gerhoh of Reichersberg follow Burchard without major changes. The variants listed by Hampe and Werminghoff indicate that they both distinguished between the basic text of the oath in the oldest, ninth-century MS, Würzburg M. p. theol. fol. 46 (and its descendants, the Monacenses 6241 and 27246, saec. x-xi), and the oath's transmission by Burchard and the above-named authors who depend on Burchard. And Hampe assigns the twelfth-century Vaticanus 1348 to the Burchard tradition, when he says that its readings largely correspond with Burchard's (‘paene omnibus conveniunt Burchardi Wormat. decret. …’). Both scholars are fully conversant with the textual history of the document; they reprint in the notes the abbreviated version of the oath in Gratian's Decretum, and the text in a Roman Ordo which represents a version re-written in accordance with certain concepts of Roman law. The Burchard-tradition has been discussed in a recent study. Some of the changes made by Burchard in the original text of the oath are readily understandable. The variant in … conspectu, instead of in … basilica, probably resulted from a scribal dittography, because the same expression occurs in the oath of purgation in the lines preceding and following the correct reading. The variant adversum, instead of adversus, is an emendation of the original text. Burchard evidently recognized the resemblance between the original reading, ‘qualiter homines mali adversus me insurrexerunt and Psalm 53.5 ‘quoniam alieni insurrexerunt adversum me.’