Patristic Wisdom: Looking to the Fourth Sunday in Advent

And the Lord continued to speak Ahaz, saying, “Ask for yourself a sign from the Lord your God, up to a depth or up to a height.” And Ahaz said, “I will not ask, and I will not test the Lord.” And he said, “Hear now, house of David! Is it not a small thing for you to put up a fight with people? And how do you put up a fight with the Lord? Because of this, the Lord himself will give you a sign: Look, the maiden will become pregnant and will bear a son, and you will call his name Immanuel. He will eat butter and honey before he knows either to prefer evil or choose the good.” Because before the child knows good or bad, he refuses wickedness to choose good; and the land that you fear because of the presence of the two kings will be forsaken. But God will bring upon you and upon your people and upon the house of your father days that have not yet come since the day when Ephraim took away the king of the Assyrians from Judah. (Isaiah 7:10–17 LXX)

And again hear what was prophesied through Isaiah the prophet, that He would be born of a virgin. He said, “Behold, the virgin shall conceive and bear a son, and they will call his name, God with us.” Through the prophetic spirit God announced beforehand that things which are unimaginable and believed to be impossible for human beings would take place, in order that when it occurred it would be believed and received by faith because it had been promised. In order to ensure that someone does not accuse us of saying the same things as the poets, who say that Zeus came to women for sexual pleasure, we will explain the words of this prophecy clearly. The phrase “behold, the virgin shall conceive” means that the virgin would conceive without intercourse. If she had in fact had intercourse with someone, she would not have been a virgin. God's power came on the virgin, overshadowed her and caused her to conceive while she remained a virgin.

Justin Martyr, First Apology 33

The Savior's name, because of which He is called “God with us” by the prophet, signifies both natures of his one person. For He who, born before time from the Father, is God Himself in the fullness of time, became Emmanuel (that is, “God with us”) in His mother's womb, because He deigned to take the weakness of our nature into the unity of His person when “the Word was made flesh and dwelt among us.” In a wonderful manner He began to be what we are, while not ceasing to be what He had been, assuming our nature in such a way that He Himself would not lose what He had been.

Bede, Homilies on the Gospels 1.5

Now, since the Lord was not a mere man but was also God and knew all things, He stood in no need of reflection, inquiry, counsel or judgment. He also had a natural affinity for good and antipathy for evil. Thus it is in this sense that the prophet Isaiah, too, says, “Before the child shall know to refuse the evil, He will choose the good. For before the child knows to refuse the evil and to choose the good, He will reject the evil by choosing the good.” The “before” shows that He made no inquiry or investigation in a human manner but that since He was God and divinely subsisted in the flesh—that is to say, was personally united to the flesh—by the fact of His very being and His knowing all things He naturally possessed the good.

John of Damascus, Orthodox Faith 3.14