Legend suggests the St. Gregory the Great (d. 604) read the initial a few lines chanted by angels on a specific Easter morning in Rome while he walked barefoot in an incredible religious procession and the saint thereupon included the fourth line: “Ora pro nobis Deum. Alleluia.” This Marian hymn https://vitapronobis87642.blogspothub.com/30505376/little-known-facts-about-vita-pro-nobis