Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.
All Commentaries on Isaiah 7:14 Go To Isaiah 7
Gregory the Theologian
AD 390
Humanity was blended with God, and he was one. The more powerful predominated in order that I might become god just as he became human. Although he was already begotten, he was born of a woman, who was a virgin. Because his birth was from a woman, it was human. Because she was a virgin, it was divine. He had neither a human father nor a divine mother.