Verbum Patris hodie (Anon., Sarum Antiphonal, 13th century), performed by Collegium Vocale Gent, conducted by Peter Dijkstra
From the Begijnhofkerk, Sint-Truiden (Flanders, Belgium)

The Word of the Father proceedeth this day from a virgin …

In case you’ve missed earlier Advent posts:
Day 1, Day 2