This article explores the subject of the Paschal Triduum, which has been at the centre of the liturgical celebration of the passion, death and resurrection of Jesus Christ since the first centuries of the Church. The author examines Liber officialis, the work of the medieval liturgist Amalarius of Metz, to show the rites used in the liturgy during the most important days for Christians in the first half of the ninth century. The paper analyses the rites described in Liber officialis and the liturgical customs of the Paschal Triduum, for which Amalarius of Metz provides rich interpretation and justification. The author of this study shows the theological, symbolic and spiritual sense of the celebrations presented in the medieval liturgical instructions. In his analysis, the author takes into account the vital importance of Amalarius’s allegorical method as this mode of interpretation reveals ingenuity and creativity, though requires a realistic assessment of the reliability of the interpretations. Amalarius’s theories from Liber officialis are examined so that the conclusions of the analysis may serve today as an aid to a better understanding of the liturgy of the Paschal Triduum.