(NOTE: I have quoted the relevant parts below, precisely as he quoted them to me in a public Facebook conversation in the group "The Biblical Worldview Defended." And my response below is the one that I shared with him in the group.):
//Isaiah 7:14 (KJV) "Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel." Christians say this verse predicts the virgin birth of Jesus, who they maintain is the deity come down to earth to be with us. However, this citation has been poorly translated, taken out of context, and is not messianic in any event. (Note, by the way, how the book of Matthew in the Christian Bible misquotes this verse).//
//Poor Translation: The Hebrew word for virgin is "betula". The root of the word is so specific that the Hebrew scriptures mention it with reference to stained bedsheets. However, the word used in Is 7:14 is "alma" which most dictionaries translate as "young woman." The word "alma" is found only seven times in scripture. In some places, it could mean either "virgin" or "young woman" but two verses suggest that an "alma" need not be virginal (Proverbs 30:19 -- "the way of a man with an alma", which is usually sexual -- and Song of Songs 6:8 -- "queens, concubines, and almas", the first two clearly not virginal, which suggests the third also is not.) To think the prophet would have used "alma" rather than the unequivocal "betula" strains credulity.//
First, there is no reason to think that "young woman" would be a better translation of almah in Proverbs 30:18-19. The writer is speaking of things that are extremely amazing (v.18). And what is more amazing than the first time that a man and a woman make love together? To translate almah as "virgin" would be quite natural here. Certainly, there is nothing here to indicate that "young woman" is preferable to "virgin."
The same is true of Song of Songs 6:8-9: "Sixty queens there may be, and eighty concubines, and virgins beyond number; but my dove, my perfect one, is unique, the only daughter of her mother, the favorite of the one who bore her." Here the contrast seems to be between his lover and all the other possible love interests, but his lover is the one who has his attention. It is certainly much more likely that almah would be translated as "virgin" here, since a Jewish writer of Scripture would not be seen as looking out on the whole field of women (including married women) for a wife. At any rate, there is absolutely nothing to favor a rendering of "young woman" over "virgin."
On the other hand, it is quite certain that when Isaac uses almah in Genesis 24:43 that he is looking for a virgin for his wife and not a young married woman. And that virgin is Rebekah. And in Exodus 2:8 there is every indication that Moses' sister is a virgin. And in Song of Songs 1:3 it is safe to assume that in the context of ancient Jewish Scripture it is virgins who are attracted to the subject of this play.
Furthermore, Isaiah 7:14 says that this will be a sign. When the LORD gives a sign, it is a miraculous sign. (See Numbers 14:22; 16:38; Deuteronomy 4:34; 6:22; 7:19; 11:3; 13:1-2; etc.)
See Isaiah 38:7-8 for Isaiah's use of the word "sign" in a similar context: "‘This is the LORD’s sign to you that the LORD will do what he has promised: I will make the shadow cast by the sun go back the ten steps it has gone down on the stairway of Ahaz.’ So the sunlight went back the ten steps it had gone down."
A "young woman" becoming pregnant and giving birth to a son would not be much of a sign, but a "virgin" conceiving and giving birth to a son is most certainly a sign.
But most importantly, the Jewish scholars who translated the Hebrew of Isaiah 7:14 into Greek when making the Septuagint (centuries before the Gospel of Matthew) chose the Greek word parthenos, which explicitly means "virgin." Do you really think that nearly 3000 years later you have a better understanding of the word almah than the elite Jewish scholars who lived in that ancient culture and who lived in much closer proximity to the time of Isaiah?
So your attempt to show that "virgin" is a "poor translation" completely fails on all accounts.
//Also, "will conceive" is unlikely. The Hebrew "hara" is most likely present tense and is better read "is pregnant."//
First, your "unlikely" and "most likely" are a matter of your own bias and not fact, and therefore of no substance. But more importantly, it really makes no difference, as Old Testament prophecy is often spoken in the present tense (as the prophets/"seers" were often seeing things in visions and speaking about them as they were happening in their visions).
//Context: This verse concerns a specific political problem of that era, and has no messianic significance at all. Isaiah writes in a highly flowery style, which makes it difficult to follow his point. However, if you read verses 1-15 slowly and carefully, you will see that Isaiah is telling his king, Ahaz, not to worry about two neighbors, Rezin and Pekah, who threaten the kingdom, because these two "firebrands" will be vanquished. How long will that take? A few years -- i.e. in the amount of time it takes a young woman to bear a child, and raise him to know the difference between good and evil.//
I agree that it is important that when reading the words of the prophets that you read them "slowly and carefully." Doing that, you will notice that God tells Ahaz to ask for a sign, but Ahaz refuses. God's response is to rebuke Ahaz and then announces a sign that is for "the house of David" (not Ahaz). The definitive proof that it is not Ahaz that the sign is given to is found in Isaiah 7:14: "Therefore the Lord himself will give you [plural] a sign...." The Hebrew word for "you" is plural (and also in the Greek Septuagint). So the sign of a virgin is a sign for the house of David, the line of the Messiah (and not for Ahaz--because Ahaz has refused to ask for a sign when the Lord tells him to do so).
//As for the name of the child, Emanuel, though Christians render it as "God with us," it should be rendered as "God is with us," a statement to King Ahaz that he will defeat his two neighbors because he, Ahaz, has a divine ally. The name is a comment about God, not a description of the person so named. (See also comments on Isaiah 9:6).//
First, either rendering of Emmanuel is acceptable, and both renderings bear the same meaning. Second, if this is meant to be a sign of God being with Ahaz in order to comfort and assure him, then why is it followed (7:17-25) with the prophecy that the Assyrians will leave his kingdom desolate? Third, who is this woman who bears a son as a sign to Ahaz and why is Emmanuel (which you say is a great sign to Ahaz) never mentioned in 2 Kings or 1 & 2 Chronicles? One would think that this son must surely be a member of Ahaz's own family, but the name never appears in any records of his lineage (the lineage of the kings being a focus of the writers of Kings and Chronicles). Since Isaiah is apparently written first, one would think that the writers of Kings and Chronicles would be especially interested in noting who this Emmanuel is. Fourth, throughout the Old Testament, the meanings of names usually bear significance for the child that is named (e.g., Genesis 3:20; 25:25-26; 35:10; 35:18).
The same things apply to the son spoken of in Isaiah 9:6-7. The son named in Isaiah 9:6-7 is clearly a king for whom "the greatness of his government and peace there will be no end. He will reign on David’s throne and over his kingdom, establishing and upholding it with justice and righteousness from that time on and forever." And yet, the writers of Kings and Chronicles never name him. And of course, none of the kings of Israel/Judah written about in Kings and Chronicles reign "forever" (except God).
//What the text says is simple. To paraphrase -- look, the young woman is pregnant and will give birth to a boy and she will call him "God is with us" he will be eating butter and honey before he knows to choose good from ill. Before he knows how to choose good from ill the lands of those people you fear will be forsaken.//
Perhaps there is a deeper meaning. Possibly even a double meaning. Perhaps what the text is actually saying is that these kings and their kingdoms will fade away. They won't even exist when the Messiah comes. Look for the coming of Messiah.
At first blush, the meaning that you have given seems more natural. But when one looks more closely, it becomes clear that there must be a very different meaning, as I believe I have shown conclusively above. Certainly, Matthew, a Hebrew scholar and First Century Jew, saw that deeper meaning and applied it to Jesus--whose miracles and prophecies, sinless life, transcendent teaching, fulfillment of many Old Testament Messianic prophecies, death and resurrection he witnessed and wrote about.
//Parenthetically, Jesus was never called "Emanuel".//
Well, actually he was. See Matthew 1:23....and billions of Christians since then! :)
MY SUMMARY RESPONSE:
(1) Your arguments against the interpretation of Isaiah 7:14 given in Matthew 1:23 fail. You fail to give any substantive argument against it. And you have failed to consider the considerable evidence for it.
(2) It remains true that the young woman spoken of in Isaiah 7:14 is an unmarried virgin. This is shown to be true by the use of the word almah in the Old Testament and by the fact that the ancient translators of the Old Testament chose to use the Greek word parthenos to translate it. Furthermore, it is shown to be so by the fact that this is given as the Yahweh's sign that he will fulfill his promise to the house of David (the messianic line): a young woman conceiving and giving birth to a son is not a sign, but a virgin conceiving and giving birth to a son is most certainly a miraculous sign from the Lord.
Additionally, you find yourself caught in an "Catch-22" situation: If Matthew is simply making up stories about Jesus (as I assume you believe), then why would he make up a story about Jesus being born of a virgin and try to sell it as the fulfillment of a messianic prophecy to the Jews to whom he is writing--unless this was the well known meaning of Isaiah 7:14 among the Jews of the First Century? That would be a ridiculous thing to do. And it is hard to see how such ridiculous claims could become accepted unless there was evidence that they were true. And if the claim that Jesus was born of a virgin was simply to satisfy a prevalent contemporary interpretation of Isaiah 7:14, why does Luke never mention Isaiah 7:14 in his narrative of the virgin birth? If however, Jesus was truly born of a virgin, then this messianic prophecy and miraculous sign from Yahweh were truly fulfilled in him; and he is your Messiah.
*MORE RESOURCES FOR STUDYING MESSIANIC PROPHECY
Gustave Dore (1832-83), Wood Engraving