Legend states the St. Gregory The nice (d. 604) heard the 1st three strains chanted by angels on a certain Easter early morning in Rome while he walked barefoot in a terrific religious procession and the saint thereupon added the fourth line: “Ora pro nobis Deum. Alleluia.” Almighty, eternal God, https://vita-pro-nobis43198.newsbloger.com/31694933/facts-about-vita-pro-nobis-revealed