The church uses, from December 17 to 24, seven short prayers that have a special richness and importance. Known as the "O Antiphons" or the "Greater Antiphons," these prayers compress and express the Old Testament Messianic hope for Christ.
Each O Antiphon is a mosaic of biblical references, collected and written in a style called anthological. The unknown author of these beautiful prayers lived around the sixth or seventh Christian century. The author chose seven titles whose first letters are
S-A-R-C-O-R-E. Read in reverse order, these letters form two Latin words [ero cras] which mean: "Tomorrow I shall be."
O Wisdom - December 17
O Sapientia , O Wisdom (Eccl 24: 5), you came forth from the mouth of the Most High (Sir 24: 30), and reaching from beginning to end, you ordered all things mightily and sweetly (Wis 8: 1). Come, and teach us the way of prudence (Isa 40: 14).
O Adonai - December 18
O Adonai or O Lord and Ruler (Exod 6: 13) and Ruler of the house of Israel (Matt 2: 6), you appeared to Moses in the fire of the burning bush (Exod 3: 2), and on Mount Sinai gave him your Law (Exod 20). Come, and with outstretched arm redeem us (Jer 32: 21).
O Radix Jesse - December 19
O Root of Jesse, you stand for the ensign of all mankind (Isa 11: 10); before you kings shall keep silence and to you all nations shall have recourse (Isa 52: 15). Come, save us, and do not delay (Hab 2: 3).
O Clavis David - December 20
O Key of David (Apoc 3: 7) Scepter of the house of Israel, you open and no man closes; you close and no man opens (Isa 22: 22). Come, and deliver him from the chains of prison who sits in darkness and in the shadow of death (Ps 107: 10).
O Oriens - December 21
O Rising Dawn (Zac 6: 12), Radiance of the Light eternal (Hab 3: 4) and Sun of Justice (Mal 3: 20); Come, enlighten those who sit in darkness & the shadow of death (Ps 107: 10; Lk 1: 78).
O Rex Gentium - December 22
O King of the Gentiles (Hag 2: 8), Desired of all, you are the cornerstone that binds two into one (Eph 2: 20). Come, and save poor man whom you fashion out of clay (Gen 2: 7).
O Emmanuel - December 23 O Emmanuel (Isa 7: 14; 8: 8), our King and Lawgiver (Gen 49:10; cf. Ezek 21: 32), the Expected of the nations and their Savior (Isa 33: 22): Come, and save us, O Lord our God.