Legend states the St. Gregory The nice (d. 604) heard the 1st three strains chanted by angels on a certain Easter morning in Rome though 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://jeffreyoyejo.verybigblog.com/30638703/the-basic-principles-of-vita-pro-nobis