5 Let no man in poorness of soul entertain this conceit, and turn over such most beggarly thoughts in his mind, and say to himself, “How 'in the beginning was the Word, and the Word was with God, and the Word was God: all things were made by Him;' and lo, 'the Word was made flesh, and dwelt among us?'” Hear why it was done. “To those” we know “who believed on Him He has given power to become the sons of God.” Let not those then to whom He has given power to become the sons of God, think it impossible to become the sons of God. “The Word was made flesh, and dwelt among us.” Do not imagine that it is too great a thing for you to become the sons of God; for your sakes He became the Son of man, who was the Son of God. If He was made, that He might be less, who was more; can He not bring it to pass, that of that less which we were, we may be something more? He descended to us, and shall not we ascend to Him? For us He accepted our death, and shall He not give us His Life? For you He suffered your evil things, and shall He not give you His good things?
6. “But how,” one will say, “can it be, that the Word of God, by whom the world is governed, by whom all things both were, and are created, should contract Himself into the womb of a Virgin; should abandon the world, and leave the Angels, and be shut up in one woman's womb?” Thou skillest not to conceive of things divine. The Word of God (I am speaking to you, O man, I am speaking to you of the omnipotence of the Word of God) could surely do all, seeing that the Word of God is omnipotent, at once remain with the Father, and come to us; at once in the flesh come forth to us, and lay concealed in Him. For He would not the less have been, if He had not been born of flesh. He “was” before His own flesh; He created His own mother. He chose her in whom He should be conceived, He created her of whom He should be created. Why do you marvel? It is God of whom I am speaking to you: “The Word was God.”
Source: Sermons on Selected Lessons of the New Testament (New Advent)