The large letter P signals the opening hymn for the feast of Saint Peter Martyr, celebrated on April 29: "Protexisti me deus a conve[n]tu malignantium.." (Thou hast protected me, God, from the assembly of the malignant). Peter Martyr (1204–1252) was a Dominican friar and priest, a native of Verona, who spoke out against heresy and became a contemporary hero to Dominicans. The choral liturgy for Saint Peter Martyr was quickly composed after his canonization in 1253, and this illumination to accompany it is one of the earliest scenes of his martyrdom to survive. The depiction of Saint Peter Martyr's execution at the hands of two assailants, Carino and Porro, borrows from the established tradition for representing Saint Thomas Becket: the executioners are dressed as knights, and the saint kneels down in prayer in an interior space. Stylistic details of the initials and the combinations of colors suggest that the Gradual this leaf is from was produced in southern Italy; further research should explore a possible link to the Church of San Domenico Maggiore in Naples.