Isaiah 7:14

Therefore the Lord himself shall give you a sign
Whether they would ask one or not; a sign both in heaven and earth, namely, the promised Messiah; who being the Lord from heaven, would take flesh of a virgin on earth; and who as man, being buried in the heart of the earth, would be raised from thence, and ascend up into heaven; and whose birth, though it was to be many years after, was a sign of present deliverance to Judah from the confederacy of the two kings of Syria and Israel; and of future safety, since it was not possible that this kingdom should cease to be one until the Messiah was come, who was to spring from Judah, and be of the house of David; wherefore by how much the longer off was his birth, by so much the longer was their safety. Behold, a virgin shall conceive, and bear a son;
this is not to be understood of Hezekiah, the son of Ahaz, by his wife, as some Jewish writers interpret it; which interpretation Jarchi refutes, by observing that Hezekiah was nine years old when his father began to reign, and this being, as he says, the fourth year of his reign, he must be at this time thirteen years of age; in like manner, Aben Ezra and Kimchi object to it; and besides, his mother could not be called a "virgin": and for the same reason it cannot be understood of any other son of his either by his wife, as Kimchi thinks, or by some young woman; moreover, no other son of his was ever lord of Judea, as this Immanuel is represented to be, in ( Isaiah 8:8 ) nor can it be interpreted of Isaiah's wife and son, as Aben Ezra and Jarchi think; since the prophet could never call her a "virgin", who had bore him children, one of which was now with him; nor indeed a "young woman", but rather "the prophetess", as in ( Isaiah 8:3 ) nor was any son of his king of Judah, as this appears to be, in the place before cited: but the Messiah is here meant, who was to be born of a pure virgin; as the word here used signifies in all places where it is mentioned, as ( Genesis 24:43 ) ( Exodus 2:8 ) ( Psalms 68:25 ) ( Song of Solomon 1:3 ) ( 6:8 ) and even in ( Proverbs 30:19 ) which is the instance the Jews give of the word being used of a woman corrupted; since it does not appear that the maid and the adulterous woman are one and the same person; and if they were, she might, though vitiated, be called a maid or virgin, from her own profession of herself, or as she appeared to others who knew her not, or as she was antecedent to her defilement; which is no unusual thing in Scripture, see ( Deuteronomy 22:28 ) to which may be added, that not only the Evangelist Matthew renders the word by (paryenov) , "a virgin"; but the Septuagint interpreters, who were Jews, so rendered the word hundreds of years before him; and best agrees with the Hebrew word, which comes from the root (Mle) , which signifies to "hide" or "cover"; virgins being covered and unknown to men; and in the eastern country were usually kept recluse, and were shut up from the public company and conversation of men: and now this was the sign that was to be given, and a miraculous one it was, that the Messiah should be born of a pure and incorrupt virgin; and therefore a "behold" is prefixed to it, as a note of admiration; and what else could be this sign or wonder? not surely that a young married woman, either Ahaz's or Isaiah's wife, should be with child, which is nothing surprising, and of which there are repeated instances every day; nor was it that the young woman was unfit for conception at the time of the prophecy, which was the fancy of some, as Jarchi reports, since no such intimation is given either in the text or context; nor did it lie in this, that it was a male child, and not a female, which was predicted, as R. Saadiah Gaon, in Aben Ezra, would have it; for the sign or wonder does not lie in the truth of the prophet's prediction, but in the greatness of the thing predicted; besides, the verification of this would not have given the prophet much credit, nor Ahaz and the house of David much comfort, since this might have been ascribed rather to a happy conjecture than to a spirit of prophecy; much less can the wonder be, that this child should eat butter and honey, as soon as it was born, as Aben Ezra and Kimchi suggest; since nothing is more natural to, and common with young children, than to take down any kind of liquids which are sweet and pleasant. And shall call his name Immanuel;
which is, by interpretation, "God with us", ( Matthew 1:23 ) whence it appears that the Messiah is truly God, as well as truly man: the name is expressive of the union of the two natures, human and divine, in him; of his office as Mediator, who, being both God and man, is a middle person between both; of his converse with men on earth, and of his spiritual presence with his people. See ( John 1:14 ) ( 1 Timothy 3:16 ) .