The edition of the First Commandment in the exegesis of the Decalogue by Ulrich von Pottenstein († 1416) provides scholarly access to the most monumental document of late medieval Latin-vernacular expository writing in the German-speaking area. The critical edition of the text draws upon all extant manuscripts. The Latin sources exploited by Ulrich for his learned katechesis (Thomas Aquinas' "Decretum Gratiani" and "Summa theologiae" and Guillelmus Peraldus' "Summa de vitiis et virtutibus") are documented in detail in the commentary section. An introduction covering all aspects of the relevant research provides information on the author and his work.