A very special feature of the Liturgy for the last week of Advent is the Great O Antiphons. These are seven prayers that are recited or chanted as the antiphon before the Magnificat at Evening Prayer from the 17th to the 23rd of December. The origin and age of these texts is unknown. However, sometime around the 8th century, monastic communities throughout western Europe were using them at evening worship services during the season of Advent and this spread to the whole Roman church.
Each one begins with the acclamation “O,” and addresses Christ by one of His messianic titles from the Old Testament, (Wisdom, Mighty Lord, Root of Jesse, Key of David, Radiant Dawn, King of the Nations and Emmanuel) and ends with a heartfelt plea for His coming. While using Christ’s messianic titles they look to His future coming and because they are from the Old Testament they also hearken to the past at the same time. In this they reflect the duality of the season as a whole.
One of the most interesting features involves a kind of encoded message via these antiphons. The initials of each of these titles in Latin (Sapientia, Adonai, Radix Jesse, Clavis David, Oriens, Rex Gentium, and Emmanuel) combine to form the word “SARCORE”. When this is arranged backwards, it spells the phrase “ERO CRAS“, which means “Tomorrow, I will be.” This coincidence was very suggestive to people in the Middle Ages because the beginning of the celebration of the mystery of the Incarnation on Christmas Eve (December 24th) falls on the day after the singing of the antiphons. Thus the antiphons become like building blocks that when combined reiterate the promise of our God to be with us.
The Roman Catholic Diocese of Hexham and Newcastle has produced a booklet to help guide your prayers. It can be downloaded here.