Noting how an hypothesis can turn into a truth simply by being repeated, this article examines carefully the basis for the date normally given for this sermon and the frailty of the textual tradition that is the basis for the Morin edition of this sermon. After a careful analysis of the factors that might help to date it, it is assigned an uncertain date. It remains, however, plausible to think that it was delivered ad mensam Cypriani. The analysis of the (...) transmission of this sermon includes several new manuscripts, a new stemma and several general observations about its transmission. This article concludes with comments about the content and a new edition of the Latin text of the sermon. (shrink)