"And the Word became flesh . . ." (John 1:14). How can the Godhead be in the flesh? And why? For the Sixth Day of Christmas, here is Basil of Caesarea’s (330-379) answer:
God is on earth, God is among us, not now as lawgiver–there is no fire, no trumpet blast, no smoke-wreathed mountain, dense cloud, or storm to terrify, whoever hears him–but as one gently and kindly conversing in a human body with his fellow men and women. God is in the flesh. Now he is not acting intermittently as he did through the prophets. He is bringing back to himself the whole human race, which he has taken possession of and united to himself. By his flesh he has made the human race his own kin.
But how can glory come to all through only one? How can the Godhead be in the flesh? In the same way as fire can be in iron: not by moving from place to place but by the one imparting to the other its own properties. Fire does not speed toward iron, but without itself undergoing any change it causes the iron to share in its own natural attributes. The fire is not diminished and yet it completely fills whatever shares in its nature. So it is also with God the Word. He did not relinquish his own nature and yet he dwelt among us. He did not undergo any change and yet the Word became flesh. Earth received him from heaven, yet heaven as not deserted by him who holds the universe in being.
Let us strive to comprehend the mystery. The reason God is in the flesh is to kill the death that lurks there. As diseases are cured by medicines assimilated by the body, and as darkness in a house is dispelled by the coming of light, so death, which held sway over human nature, is done away with the coming of God. And as ice formed on water covers its surface as long as night and darkness last but melts under the warmth of the sun, so death reigned until the coming of Christ; but when the grace of God our savior appeared and the Sun of Justice rose, death was swallowed up in victory, unable to bear the presence of true life. How great is God’s goodness, how deep his love for us.
– ‘Homily on Christ’s Ancestry’