“Now then I pray you accept His Conception, and leap before Him; if not like John from the womb (Luke 1:41), yet like David, because of the resting of the Ark (2 Samuel 6:14). Revere the enrollment on account of which you were written in heaven, and adore the Birth by which you were loosed from the chains of your birth (Luke 2:1-50), and honour little Bethlehem, which has led you back to Paradise; and worship the manger through which thou, being without sense, wast fed by the Word. Know as Isaiah bids you, your Owner, like the ox, and like the ass your Master’s crib; if you be one of those who are pure and lawful food, and who chew the cud of the word and are fit for sacrifice. Or if you are one of those who are as yet unclean and uneatable and unfit for sacrifice, and of the gentile portion, run with the Star, and bear your Gifts with the Magi, gold and frankincense and myrrh (Isaiah 1:3), as to a King, and to God, and to One Who is dead for you. With Shepherds glorify Him; Matthew ii with Angels join in chorus; with Archangels sing hymns. Let this Festival be common to the powers in heaven and to the powers upon earth (Luke 2:14-15). For I am persuaded that the Heavenly Hosts join in our exultation and keep high Festival with us today… because they love men, and they love God just like those whom David introduces after the Passion ascending with Christ and coming to meet Him, and bidding one another to lift up the gates.” St. Gregory the Theologian, Oration 38.27.
Have you ever wondered why in the icons of the nativity we see an ox and a donkey? If you look closely at the icon above you can see that next to the crib there is an ox and an ass depicted. The symbolic imagery goes back to the very beginning of Christian depictions of the Lord. In it, the fathers of the Church see the coming together of all nations in the person of Christ Who is The Logos become a human being. The Ox is the clean animal and the Donkey represents the unclean animals. As a result these two animals represent the ancient Jewish division of the peoples of the world from the biblical perspective (the Old Testament). Christ’s birth in the flesh is a bringing together of all nations and a union of God and man. He condescends and becomes what we are that we might become what He is, regardless of the nation we come from or our previous life. Christ brings together all things in Himself.
For a beautiful and excellent discussion of this icon in much more detail, I would direct you to this video by the Orthodox Iconographer and Icon Carver, Jonathan Pageau: Christmas as The Anchor of Reality