The library of the Wroclaw University houses a manuscript BUWr I Q 377, which comprises a compilation of exemplary sermons of Jan Frankenstein, an outstanding 15th century intellectual, preacher, Wroclaw inquisitor engaged in late medieval movement of Church renewal. Although the manuscript has been frequently mentioned in historiography, a considerable part of the sermons has not been reviewed yet. The present article is devoted to the genesis of two of the above mentioned sermons. Sermons "Scio quid faciam" refer to the same topic and their contents are to a large extent the same (although one is 15 pages long, while the other is 5). These are sermons intended for the time of plague and they contain advice pertaining to life and priestly service in the infected city. They were prepared during the plague of 1439 in Wroclaw to raise the moral level of the Dominican Fathers and written by Frankenstein as two versions of a model text for the time of plague.