Legend states the St. Gregory the Great (d. 604) read the 1st three lines chanted by angels on a specific Easter early morning in Rome though he walked barefoot in a great religious procession and the saint thereupon included the fourth line: “Ora pro nobis Deum. Alleluia.” This Marian hymn https://vita-pro-nobis87532.bloggactif.com/32104143/how-vita-pro-nobis-can-save-you-time-stress-and-money