John wrote, "The Word became flesh and dwelt among us, and we have seen his glory, glory as of the only Son from the Father, full of grace and truth" (John 1:18)

Consider what Reformed theologian Karl Barth has written about the Word became flesh:

In the statement, "the Word was made flesh," the Word is the subject. Nothing befalls Him; but in the becoming asserted of Him he acts.

The becoming asserted of Him is not, therefore, to be regarded as an element in the world process as such. It rests upon no inner necessity of human history, nor is it to be understood as having its source in any such necessity. There is no condition of the world or man which can form the basis of a claim or capacity whereby this becoming can have been predicted.

This becoming cannot be brought into connexion with creation. It cannot be regarded as one of its evolutionary possibilities. No such idea is tolerable even if this becoming is not the divine reaction to the Fall. A higher evolution of the world created by God, to the extent of bringing forth His own Word as one of the elements in its own substance, is also a quite impossible idea even apart from the Fall.

God's Word becoming a creature must be regarded as a new creation. How much more so, since man and man's history are stamped and hallmarked by the Fall. How could Christ ever become possible as the product of an immanent world evolution? No, the Word's becoming flesh is not a movement of the creature's own. Like creation itself, it is a sovereign divine act, and it is an act of lordship different from creation.

Karl Barth, Church Dogmatics, edited by G. W. Bromiley and T. F. Torrance, I/2 (Edinburgh: T. & T. Clark, 1956), p. 134, emphasis added.

So let us rejoice again at Christmas that the Word of God became flesh and dwelt among us and that we have seen his glory.