Why did God, "the Word of God Himself, Who is before all worlds, the Invisable, the Incomprehensible, the Bodiless, Beginning of Beginning, Light of Light, the Source of Life and Immortality, the Image of Archetypal Beauty, the unmovable Seal, the unchangeable Image, the Father's Definition and Word," become man? Why did He take on our human flesh, our human will, all aspects of our humanness except for sin?
Saint Gregory the Theologian says,
He partakes of my flesh that He may both save the image and make the flesh immortal... The Good Shepherd, He who lays down His life for His sheep, came to seek that which had strayed...He humbles Himself, that He may raise up with Himself the soul that was tottering to a fall under a weight of sin....[for] my perfection and return to the first condition of Adam.
Often we only think of baby Jesus, a precious child of Mary and Joseph who are normally show standing over the manger like two young adoring parents. We forget that this was not a normal birth. We forget that the seed in conception came from the Holy Spirit and the birth was from a virgin. We forget that Joseph was not the father. We forget that He was much older than Mary and was chosen as the protecter of Mary so she could live life as a virgin. We forget that this child is God, the Creator of the universe. We forget why we celebrate this event as it gets hurried with all the worldly activities that have become associated with this time of year. The gift giving and receiving, the many parties, the decorations, the children stories about snowmen and reindeer all seem to dominate this event. The idea that God actually became man while remaining fully God is lost in all the activities.
Saint Gregory writes,
Adore the birth by which you were loosed from the chains of your birth, and honor little Bethlehem, which has led you back to Paradise.... With shepherds glorify Him; with angels join in chorus;with archangels sing hymns. Let this Festival be common to the powers upon earth.
Reference: On the Manisfestation of God in the Birth of the Christ, Oration 38 of Saint Gregory the Theologian