Legend states the St. Gregory The nice (d. 604) heard the 1st three traces chanted by angels on a certain Easter morning in Rome though he walked barefoot in a fantastic spiritual procession and that the saint thereupon extra the fourth line: “Ora pro nobis Deum. Alleluia.” Almighty, everlasting God, https://vitapronobis08642.elbloglibre.com/31080061/the-2-minute-rule-for-vita-pro-nobis