Legend states the St. Gregory The nice (d. 604) heard the main three strains chanted by angels on a certain Easter morning in Rome while he walked barefoot in a terrific spiritual procession and that the saint thereupon extra the fourth line: “Ora pro nobis Deum. Alleluia.” Almighty, everlasting God, https://milowekos.blogprodesign.com/52876044/a-simple-key-for-vita-pro-nobis-unveiled