Legend suggests the St. Gregory the Great (d. 604) read the very first a few lines chanted by angels on a specific Easter morning in Rome even though he walked barefoot in an excellent spiritual procession and that the saint thereupon added the fourth line: “Ora Professional nobis Deum. Alleluia.” https://vitapronobis43108.ezblogz.com/62839485/vita-pro-nobis-fundamentals-explained