St. Gregory the Theologian, Oration 38, Section 17:
Now welcome for me his conception and leap for joy, if not indeed like John in the womb, then like David when the ark came to rest. Be awed at the census record through which you have been recorded in heaven, and revere the birth through which you have been released from the bonds of birth, and honor little Bethlehem, which has brought you back to paradise, and bow before the manger. you who were without reason have been fed by the Word. Know, like the ox, your owner — Isaiah exhorts you — and like the donkey know your master’s crib, whether you are among those who are pure and under the law and chew the cud of the Word and are prepared for sacrifice, or whether up to now you are among the impure and unfit for food or sacrifice and belong to the Gentiles. Run after the star, and bring gifts with the magi, gold and frankincense and myrrh, as to a king and a God and one dead for your sake. With the shepherds give glory, with the angels sing hymns, with the archangels dance. Let there be a common celebration of the heavenly and earthly powers. For I am persuaded that they rejoice and celebrate with us today, if indeed they love humankind and love God, just as David represents them ascending with Christ after his Passion as they come to meet him and exhort each other to lift up the gates.