For the one and the same Spirit of God, who proclaimed by the prophets what and of what sort the advent of the Lord should be, did by these elders give a just interpretation of what had been truly prophesied; and He did Himself, by the apostles, announce that the fullness of the times of the adoption had arrived, that the kingdom of heaven had drawn near, and that He was dwelling within those that believe in Him who was born Emmanuel of the Virgin. To this effect they testify, [saying,] that before Joseph had come together with Mary, while she therefore remained in virginity, "she was found with child of the Holy Ghost;" [Matthew 1:18] and that the angel Gabriel said to her, "The Holy Ghost shall come upon you, and the power of the Highest shall overshadow you; therefore also that holy thing which shall be born of you shall be called the Son of God;" [Luke 1:35] and that the angel said to Joseph in a dream, "Now this was done, that it might be fulfilled which was spoken by Isaiah the prophet, Behold, a virgin shall be with child." [Matthew 1:23] But the elders have thus interpreted what Esaias said: "And the Lord, moreover, said to Ahaz, Ask for yourself a sign from the Lord your God out of the depth below, or from the height above. And Ahaz said, I will not ask, and I will not tempt the Lord. And he said, It is not a small thing for you to weary men; and how does the Lord weary them? Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son; and you shall call His name Emmanuel. Butter and honey shall He eat: before He knows or chooses out things that are evil, He shall exchange them for what is good; for before the child knows good or evil, He shall not consent to evil, that He may choose that which is good." [Isaiah 7:10-17] Carefully, then, has the Holy Ghost pointed out, by what has been said, His birth from a virgin, and His essence, that He is God (for the name Emmanuel indicates this). And He shows that He is a man, when He says, "Butter and honey shall He eat;" and in that He terms Him a child also, [in saying,] "before He knows good and evil;" for these are all the tokens of a human infant. But that He "will not consent to evil, that He may choose that which is good,"— this is proper to God; that by the fact, that He shall eat butter and honey, we should not understand that He is a mere man only, nor, on the other hand, from the name Emmanuel, should suspect Him to be God without flesh.
(Verse 15) He shall eat butter and honey, so that he may know how to refuse the evil and choose the good. For before he knows to refuse the evil and choose the good, the land that you dread will be forsaken by both her kings. The Lord will bring the king of Assyria upon you and your people and your father's house—days that have not come since the day that Ephraim departed from Judah. And it shall come to pass in that day, that the Lord shall hiss for the fly that is in the uttermost part of the rivers of Egypt, and for the bee that is in the land of Assyria. And they shall come, and shall rest all of them in the desolate valleys, and in the holes of the rocks, and upon all thorns, and upon all bushes. I will say something even more amazing, so that you do not think that he is born in a fantasy, he will use foods of infancy, he will eat butter and milk. And although many centuries later the Evangelist testifies about him: But the child grew in wisdom and age and grace before God and men (Luke 2:52): and this is said to confirm the truth of the human body: yet still wrapped in swaddling clothes, and fed with butter and honey, he will have the ability to judge between good and evil, so that he may reject evil and choose good. Not because he did or disapproved or chose this, but because he knew how to disapprove and choose, so that through these words we may know that the infancy of the human body did not hinder divine wisdom. Lastly, the Angels announce to the shepherds the laying in the manger: The Magi adore coming from the East, whom it is to be believed were certainly chosen. And on the other hand, Herod, the scribes, and the Pharisees are disapproved, (Matthew 2), because they killed many thousands of infants for the sake of one child.
This is said [“The child grew in wisdom and in age before God and men”] in order to establish the truth of his human body. Nevertheless, wrapped in swaddling clothes and fed with curds and honey, he will have the judgment to distinguish between good and evil, that rejecting evil he might choose the good. It does not say that he will in fact reject and choose but that he would learn to reject and to choose, so that we might know through such words that this pertains to the infant’s human body, not to divine wisdom. Finally, it must be believed that the angels who announced to shepherds the news of the infant lying in a manger and the magi who came from the east to worship him were chosen. Herod, the scribes and the Pharisees, on the other hand, were condemned because they slaughtered thousands of children for the sake of one infant.
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.
[AD 202] Irenaeus on Isaiah 7:10-17