The Roman Church has been singing the "O" Antiphons since at least the eighth century. They are the antiphons that accompany the Magnificat canticle of Evening Prayer from December 17-23.

They are a magnificent theology that uses ancient biblical imagery drawn from the messianic hopes of the Old Testament to proclaim the coming Christ as the fulfillment not only of Old Testament hopes, but present ones as well.

Their repeated use of the imperative "Come!" embodies the longing of all for the Divine Messiah.

Beginning on December 17th, pray each O Antiphon with your family daily.

DECEMBER 17TH - O’ Sapientia (meaning O Wisdom), from Isaiah 11:2-3
O Wisdom of our God Most High,
guiding creation with power and love:
come to teach us the path of knowledge!

DECEMBER 18TH - O’ Adonai (O  Leader/Ruler),  Isaiah 11:4-5 and 33:22.
O Leader of the House of Israel,
giver of the Law to Moses on Sinai:
come to rescue us with your mighty power!

DECEMBER 19TH - O’ Radix (O Root of Jesse), Isaiah 11:1
O Root of Jesse’s stem,
sign of God’s love for all his people:
come to save us without delay!

DECEMBER 20TH - O’ Clavis (O Key of David), Isaiah 22:22
O Key of David,
opening the gates of God’s eternal Kingdom:
come and free the prisoners of darkness!

DECEMBER 21ST - O’ Oriens (O Radiant Dawn), Isaiah 9:1
O Radiant Dawn,
splendor of eternal light, sun of justice:
come and shine on those who dwell in darkness and in the
shadow of death.

DECEMBER 22ND - O’ Rex Gentium (O King of the Nations),  Isaiah 2:4
O King of all nations and keystone of the Church:
come and save man, whom you formed from the dust!

DECEMBER 23RD - O’ Emmanuel (O God with Us), Isaiah 7:14
O Emmanuel, our King and Giver of Law:
come to save us, Lord our God!

—From Catholic Household Blessings & Prayers