The O Antiphons are seven verses in the Liturgy of the Hours that contain powerful pleas for the coming of the Lord. They are chanted or recited during Vespers on the last seven days of Advent. They are:
Dec. 17: O Sapientia (O Wisdom, O holy Word of God, you govern all creation with your strong yet tender care. Come and show your people the way to salvation.)
Dec. 18: O Adonai (O Sacred Lord of ancient Israel, who showed yourself to Moses in the burning bush, who gave him the holy law on Sinai mountain: Come, stretch out your strong hand to set us free.)
Dec. 19: O Radix Jesse (O Flower of Jesse' s stem, you have been raised up as a sign for all peoples; kings stand silent in your presence; the nations bow down in worship before you. Come, let nothing keep you from coming to our aid.)
Dec. 20: O Clavis David (O Key of David, O royal Power of Israel controlling at your will the gate of heaven: Come, break down the prison walls of death for those who dwell in darkness and the shadow of death, and lead your captive people into freedom.)
Dec. 21: O Oriens (O Radiant Dawn, splendor of eternal light, sun of justice: Come, shine on those who dwell in darkness and the shadow of death.)
Dec. 22: O Rex Gentium (O King of all the Nations, the only joy of every human heart; O keystone of the mighty arch of man, come and save the creature you fashioned from the dust.)
Dec. 23: O Emmanuel (O Emmanuel, king and lawgiver, desire of the nations, Savior of all people, come and set us free, Lord our God.)
If you take the first letter of each Latin title starting backward at Dec. 23, you will form the Latin words, Ero Cras, which mean, "Tomorrow I will come."
The O Antiphons inspired many Advent hymns, the most familiar of which is: "O Come, O Come Emmanuel," which incorporates the O Antiphons into its verses.