These seven antiphons are used as the Alleluia verse during Mass and as the antiphon at the Magnificat during Vespers. When combined together they make up the ancient hymn Veni, veni Emmanuel, “O come, O come, Emmanuel” (which happens to be one of my absolute favorites).
The O Antiphons begin a novena, of sorts, culminating with the Solemnity of the Nativity of the Lord, Christmas Day.
The antiphons begin as follows, in the order they are used:
O Sacred Lord
O Flower of Jesse’s Stem
O Key of David
O Radiant Dawn
O King of all the Nations
O Emmanuel (“God with us”)
The ever-clever Medievals noticed something especially powerful when the order of the antiphons reversed: Emmanuel, Rex, Oriens, Clavis, Radix, Adonai and Sapientia. The first letter of each of the antiphons spells Ero cras, Latin for “Tomorrow, I will come;” tomorrow, of course, being Christmas.
The antiphons, then, are a poetic reminder of the promised Messiah who has come to us and will to us again. Come, Lord Jesus! Do not delay!