Vespers on Christmas Eve in a Roman Catholic Church is not for that day, but the one that follows: it is the First Vespers of Christmas. This applies to any evening before a solemnity, and to all Saturday evenings.
The Church is here retaining an ancient Jewish custom—for Jews begin their Sabbath at sunset on a Friday. Those of us who have taught Jewish pupils whose families are strictly Orthodox know that in winter they have to leave their school or college early, to be home before sunset.
This hymn is said or sung at the First Vespers of Christmas. The near-Classical diction, and the absence of rhyme, indicates an early date of origin: the Ambrosian style. As usual with Latin poetry, it becomes clearer when said aloud.
I
Jesu redemptor omnium,
Quem lucis ante originem
Parem paternae gloriae
Pater supremus edidit.
II
Tu lumen et splendor Patris,
Tu spes perennis omnium,
Intende quas fundunt preces
Tui per orbem servuli.
III
Memento, rerum Conditor,
Nostri quod olim corporis
Sacrata ab alvo virginis
Nascendo formam sumpseris.
IV
Testatur hoc praesens dies,
Currens per anni circulum,
Quod solus e sinu Patris
Mundi salus adveneris.
V
Hunc astra, tellus, aequora,
Hunc omne quod caelo subest,
Salutis auctorem novae
Novo salutat cantico.
VI
Et nos, beata quos sacri
Rigavit unda sanguinis,
Natalis ob diem tui
Hymni tributum solvimus.
VII
Jesu, tibi sit gloria,
Qui natus es de Virgine,
Cum Patre, et almo Spiritu
In sempiterna saecula.
Author: Unknown. Date: Probably sixth century.
Notes:
II Intende…: Hear…
III alvo: from alvus,-i, fem. Here=womb.
IV Mundi salus: predicative: lit. as the saving of the world.
VI rigavit: here has the meaning of both washing and refreshing.
VII This verse, a doxology, is added to all hymns of this metre in the Christmas season, i.e. till the 5th January.