O Radix Jesse

O Radix Jesse, qui stas in signum populorum,
super quem continebunt reges os suum,
quem Gentes deprecabuntur:
veni ad liberandum nos, jam noli tardare.

O Root of Jesse, standing as a sign among the peoples;
before you kings will shut their mouths,
to you the nations will make their prayer:
Come and deliver us, and delay no longer.

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]”.