Here is a an edited version of a homily for the Nativity, by St. Basil the Great. I cannot find the full text online. If any of you know a website where it can be found so we may be blessed by the full text, attach the link in the comments section.
God on earth, God amongst us! It is no longer the God who gives the Law amidst lightning and thunder, at the sound of the trumpet on the mountain wrapped in smoke (Ex 19.18), at the heart of a fearful tempest (Ex 19.18), but he who converses gently and kindly with his brethren in a human body. God in our flesh! This is no longer he who only acts at certain times, as with the prophets, but he who assumes human nature completely and who, through the flesh that is our own, raises all humanity to himself.
How is it that light has come into all of us by means of one alone? In what way is divinity present in the flesh? It is like fire in iron…: while still remaining in place, the fire communicates its own proper ardour to the iron. It is not at all made less by this but it wholly fills the iron to which it communicates itself. In the same way God, the Word who “dwelt among us”, did not go out from himself; the Word made flesh underwent no change; heaven was not deprived of him who contained it and earth welcomed him who remains in heaven…
Enter fully into this mystery: God has come in the flesh to put to death the death concealed within it. Just as drugs cure us once they are assimilated by the body, so the darkness of a house is dispersed once the light comes into it, and so, too, the death that kept us in its power has been destroyed by the coming of our God. As ice formed during the night melts under the heat of the sun’s rays, so death has reigned till the coming of Christ. But when the Sun of justice arose (Mal 3.20), “death was swallowed up in victory” (1Cor 15.54); it could not withstand the presence of the true life… Let us sing glory to God with the shepherds, let us dance together with the angels, “for this day in David’s city a Savior has been born to you, the Messiah and Lord” (Lk 2.11)… Let us celebrate the salvation of the world, the birthday of all humanity.
Source: Saint Basil (c.330-379), Bishop of Caesarea in Cappadocia, “Homily for the Nativity of Christ,” 2.6