Each O antiphon addresses Christ using a Messianic title drawn from the prophecies of the Old Testament. Read backwards, the initials of each title in Latin form the words Cras ero or “Tomorrow I shall be (with you)”.
Dec. 18–O HOLY LORD of the House of Israel, who appeared to Moses in the flame of the burning bush, and gave him the law on Sinai– COME! and redeem us with outstretched arm.
Dec. 19–O ROOT OF JESSE, who stands for an ensign of the people, before whom kings shall keep silence, and unto whom the Gentiles shall make supplication– COME! to deliver us, and tarry not.
Dec. 20–O KEY OF DAVID, and Sceptre of the House of Israel, who opens and no man shuts, who shuts, and no man opens– COME! and bring forth the captive from his prison, he who sits in darkness and in the shadow of death.
Dec. 21–O DAYSPRING, brightness of the light eternal, and Sun of Justice- COME! and enlighten them that sit in darkness and in the shadow of death.
Dec. 22–O KING OF THE NATIONS and their desired One, the Cornerstone that makes both one– COME! and deliver man, whom You formed out of the dust of the earth.