Legend suggests the St. Gregory the Great (d. 604) read the first a few lines chanted by angels on a specific Easter morning in Rome though he walked barefoot in a fantastic spiritual procession and the saint thereupon included the fourth line: “Ora pro nobis Deum. Alleluia.” Almighty, everlasting God, https://archerhmrpu.jaiblogs.com/58140589/little-known-facts-about-vita-pro-nobis