Mass of St. Gregory (fol. 139r)

St. Gregory the Great, Pope Gregory I, is shown kneeling at the altar, during a Mass, with another priest. His triple tiara, an open book, and a chalice lie on the altar. Christ appears to him on the altar, and blood pours from his sacred wound into the communion chalice. Instruments of the Passion, the Arma Christi, are seen in the background. These include the cross, the ladder, the Holy Shroud, instruments of flagellation, nails, the hammer, and St. Peter's sword.

Context: The Seven Oes of Saint Gregory: O domine ihesu criste