But as Joseph considered this, behold, an angel of the Lord appeared to him in a dream, saying, “Joseph, son of David, do not fear to take Mary your wife, for that which is conceived in her is of the Holy Spirit; she will bear a son, and you shall call his name Jesus, for he will save his people from their sins.” All this took place to fulfil what the Lord had spoken by the prophet: “Behold, a virgin shall conceive and bear a son, and his name shall be called Emmanuel” (which means, God with us). (Matthew 1:20-23)
Because Jesus is both God and human, He is appropriately called “God with us” (Emmanuel). Christ’s own works reveal Him to be God in the flesh. It is His being both human and God which means He is our salvation by reuniting earth to heaven, divinity to humanity, Creator to creation. St Irenaeus wrote:
For it was for this end that the Word of God was made man, and he who was the Son of God became the Son of man, that man, having been taken into the Word, and receiving the adoption, might become the son of God. For by no other means could we have attained to incorruptibility and immortality, unless we had been united to incorruptibility and immortality. But how else could we be joined to incorruptibility and immortality, unless first incorruptibility and immortality had become that which we also are, so that the corruptible might be swallowed up by incorruptibility, and the mortal by immortality, that we might receive the adoption of sons? (Against Heresies 3.19.1) (HEARING THE SCRIPTURES, p 174)
So we rejoice in the Feast of the Nativity of our Lord, God and Savior Jesus Christ, singing:
COME, LET US GREATLY REJOICE IN THE LORD AS WE TELL OF THIS PRESENT MYSTERY! THE DIVIDING WALL HAS BEEN DESTROYED; THE FLAMING SWORD TURNS BACK, THE CHERUBIM WITHDRAW FROM THE TREE OF LIFE, AND I PARTAKE OF THE DELIGHT OF PARADISE FROM WHICH I WAS CAST OUT THROUGH DISOBEDIENCE. FOR THE EXPRESS IMAGE OF THE FATHER, THE IMPRINT OF HIS ETERNITY, TAKES THE FORM OF A SERVANT, AND WITHOUT UNDERGOING CHANGE HE COMES FORTH FROM AN UNWEDDED MOTHER. FOR WHAT HE WAS, HE HAS REMAINED: TRUE GOD, AND WHAT HE WAS NOT, HE HAS TAKEN UPON HIMSELF, BECOMING MAN THROUGH LOVE FOR MANKIND. UNTO HIM, LET US CRY ALOUD: O GOD BORN OF A VIRGIN, HAVE MERCY ON US!