== Origin ==
Authorship is traditionally ascribed to Saints [[Ambrose]] and [[Augustine of Hippo
|Augustine]], on the occasion of the latter's [[baptism]] by the former in AD 387.
The petitions at the end of the hymn (beginning ''Salvum fac populum tuum'') are a selection of verses from the book of [[Psalms]], appended subsequently to the original hymn.
The hymn follows the outline of the
[[Apostles' Creed ]], mixing a poetic vision of the heavenly [[liturgy]] with its declaration of faith. Calling on the name of God immediately, the hymn proceeds to name all those who praise and venerate God, from the hierarchy of heavenly creatures to those Christian faithful already in heaven to the Church spread throughout the world.
The hymn then returns to its credal formula, naming Christ and recalling his birth, suffering and death, his resurrection and glorification. At this point the hymn turns to the subjects declaiming the praise, both the universal Church and the singer in particular, asking for mercy on past sins, protection from future sin, and the hoped-for reunification with the elect.