The last of the great Antiphons addresses the Promised One as Emmanuel, which means “God with us”.
This comes from the words of the prophet Isaiah spoken to Ahaz, king of Judah (735-715 BC). Ahaz and Jerusalem were threatened by the neighboring kings because he refused to enter into an alliance against Assyria. Ahaz feared that the Davidic kingly line would be broken if his enemies prevailed. But Isaiah told him that God was on his side, and reassured him with this sign: “The virgin will conceive, and bear a son, and call his name Emmanuel” (Isaiah 7, 14)
Saint Matthew referred to this prophecy when he spoke of the angelic message Joseph received in a dream assuring him that Mary was with child through power of the Holy Spirit: “All this took place to fulfill what the Lord had said through the prophet Isaiah: ‘Behold the virgin shall be with child and bear a son, and they shall name him Emmanuel’, which means ‘God is with us’” (Matthew 1, 22-23)
And so the final great antiphon addresses the Promised One: “O Emmanuel, king and giver of the law, hope of the nations and savior of the people, come and save us, Lord our God”. (Evening Prayer December 23rd)