splendor lucis aeternae, et sol justitiae:
veni, et illumina sedentes in tenebris, et umbra mortis.
O Morning Star,
splendour of light eternal and sun of righteousness:
Come and enlighten those who dwell in darkness and the shadow of death.
From the 17th to the 23rd of December, in the final days of Advent, the antiphons for the Magnificat at Vespers are particularly elaborate. Each antiphon is a title of the Messiah, and each refers to one of Isaiah’s prophecies of the Messiah.
These “O Antiphons”, in metrical form, comprise the verses of the familiar Christmas hymn, “O come, o come, Emmanuel”. The initials of the second word in each antiphon (“Sapientia”, “Adonai”, et cetera), taken in reverse order, form the acrostic ero cras, meaning “Tomorrow, I will be [there]”.