Gratian's Decretum is one of the major works in European history, a text that in many ways launched the field of canon law. In this new volume, Atria Larson presents to students and scholars alike a critical edition of De penitentia (Decretum C.33 q.3), the foundational text on penance, both for canon law and for theology, of the twelfth century. This edition takes into account recent manuscript discoveries and research into the various recensions of Gratian's text and proposes a model for how a future critical edition of the entire Decretum could be formatted by offering a facing-page English translation. This translation is the first of this section of Gratian's De penitentia into any modern language and makes the text accessible to a wider audience. Both the Latin and the English text are presented in a way to make clear the development of Gratian's text in various stages within two main recensions. The edition and translation are preceded by an introduction relating the latest scholarship on Gratian and his text and are followed by three appendices, including one that provides a transcription of the relevant text from the debated manuscript Sankt Gallen, Stiftsbibliothek 673, and one that lists possible formal sources and related contemporary texts. This book provides a full edition and translation of the text studied in depth in Master of Penance: Gratian and the Development of Penitential Thought and Law in the Twelfth Century (CUA Press, 2014) by the same author.