O ORIENS, splendor lucis æternæ, et sol justitiæ: veni, et illumina sedentes in tenebris, et umbra mortis.Greater Advent Antiphon for December 21st. We wait in hope for Christ, who will illumine us.
O Day-Spring, Brightness of light eternal, and Sun of Justice, come and enlighten them that sit in darkness and in the shadow of death.
— Psalms 106:10 (Septuagint)
This antiphon is prayed with the Magnificat, the great canticle sung by Mary when she visited her kinswoman Elizabeth. Significantly, the canticle sung by Zachary, Elizabeth's husband and father of John the Baptist, refers back to same Psalm 106 from which this antiphon is taken.
That Christ is the new dawn is expressed in the tradition of priests saying Mass facing to the east (ad orientum).