TU TRINITATIS UNITAS
A cento. Added to the Roman Breviary in 1568. In a subsequent edition it is the hymn for Lauds on Trinity Sunday. It is made up of the first stanza of a hymn with the same opening, and of the third stanza of the composition, Æterna cœli gloria, with a doxology added.
I
O Thou Eternal One in Three,
Dread Ruler of the earth and sky,
Accept the praise we yield to Thee,
Who, waking, lift our songs on high.
II
The star that tells the approach of day
Is lingering in the glow of morn,
And night and darkness fade away—
O Holy Light, our souls adorn!
III
To God the Father throned in heaven,
To Christ the One Begotten Son,
And to the Spirit praise be given,
Now, and while endless ages run.