Legend claims the St. Gregory the Great (d. 604) listened to the first 3 lines chanted by angels on a particular Easter early morning in Rome when he walked barefoot in an excellent spiritual procession and that the saint thereupon extra the fourth line: “Ora Professional nobis Deum. Alleluia.” Almighty, https://vitapronobis09753.blogs100.com/31636345/vita-pro-nobis-things-to-know-before-you-buy