By way of introduction, recall that in what Christians now call the Septuagint (see below for more), the word "Parthenon" is used in Isaiah 7:14, which translates as "virgin" from the Greek.
First, the contention that Parthenon means only virgin is simply incorrect. The Greek word Parthenon can mean either a young woman or a virgin; for this reason Parthenon is found in the Septuagint referring to someone who is not a virgin. In Genesis 34:2-4, Shechem raped Dinah, the daughter of the patriarch Jacob, yet the Septuagint refers to her as a Parthenon after the rape: after Shechem had violated her, "his heart desired Dinah, and he loved the damsel (LXX: Parthenon) and he spoke tenderly to the damsel (LXX: Parthenon)." Clearly, Dinah was not a virgin after having been raped, and yet she was referred to as a parthenos, the very same word the Septuagint used to translate the Hebrew word alma in Isaiah 7:14.
Moreover, the Septuagint is not a Jewish document, but rather a Christian one. The original Septuagint, created 2,200 years ago by 72 Jewish translators, was a Greek translation of the Five Books of Moses alone. It therefore did not contain prophetic Books of the Bible such as Isaiah. The Septuagint as we have it today, which includes the Prophets and Writings as well, is a product of the church, not the Jewish people. In fact, the Septuagint remains the official Old Testament of the Greek Orthodox Church, and the manuscripts that consist of our Septuagint today date to the third century C.E. The fact that additional books known as the Apocrypha, which are uniquely sacred to the Roman Catholic and Orthodox Church, are found in the Septuagint should raise a red flag to those inquiring into the Jewishness of the Septuagint.
Christians such as Origin and Lucian (third and fourth century C.E.) had an enormous impact on creating and shaping the Septuagint that missionaries use to advance their untenable arguments against Judaism. In essence, the Septuagint is largely a post-second century Christian translation of the Bible, used zealously by the church throughout the centuries as an indispensable apologetic instrument to defend and sustain Christological alterations of the Jewish scriptures.
The fact that the original Septuagint translated by rabbis more than 22 centuries ago was only of the Pentateuch and not of prophetic books of the Bible such as Isaiah is confirmed by countless sources including the ancient Letter of Aristeas, which is the earliest attestation to the existence of the Septuagint. The Talmud also states this explicitly in Tractate Megillah (9a), and Josephus as well affirms that the Septuagint was a translation only of the Law of Moses in his preface to Antiquities of the Jews. Moreover, Jerome, a church father and Bible translator who could hardly be construed as friendly to Judaism, affirms Josephus' statement regarding the authorship of the Septuagint in his preface to The Book of Hebrew Questions.
In fact, Dr. F.F. Bruce, the preeminent professor of Biblical exegesis, keenly points out that, strictly speaking, the Septuagint deals only with the Pentateuch and not the whole Old Testament. Bruce writes, "The Jews might have gone on at a later time to authorize a standard text of the rest of the Septuagint, but . . . lost interest in the Septuagint altogether. With but few exceptions, every manuscript of the Septuagint which has come down to our day was copied and preserved in Christian, not Jewish, circles."
Nor, for that matter, is there any reference to a Greek translation of the Bible in all of the New Testament; and there is good reason for this. The first century church was well aware that a Jewish audience would be thoroughly unimpressed by a claim that Jesus' virgin birth could only be supported by a Greek translation of the Bible. They understood that if Jews were to find their Christian message convincing, they would need to assert that it was the actual words of the prophet Isaiah that clearly foretold Mary's virgin conception, not from the words of a Greek translation. Therefore, in Matthew 1:22-23, the author of the first Gospel insists that it was "spoken of the Lord by the prophet, saying, 'Behold, a virgin shall be with child . . . .' " Matthew loudly makes the point that it was specifically the prophet's own words that proclaimed the virgin birth, not the words of any translator.
Isaiah, of course, did not preach or write in Greek, and therefore the word parthenos never left the lips of the prophet throughout his life. All 66 chapters of the Book of Isaiah were spoken and then recorded in the Hebrew language alone. Matthew, however, was attempting to place in the mind of his intended Jewish reader that it was the words of prophet Isaiah himself which declared that the messiah would be born of a virgin. Nothing of course could be further from the truth.
The mistranslation of the Hebrew word alma as ?virgin? is evidenced by the fact that the context of Isaiah 7:14 is not speaking of the birth of a messiah at all. This fact remains obvious even to the most casual reader of the seventh chapter of Isaiah. The seventh chapter of the Book of Isaiah begins by describing the military crisis that was confronting King Ahaz of the Kingdom Judah. In about the year 732 B.C.E. the House of David was facing immanent destruction at the hands of two warring kingdoms: the northern Kingdom of Israel and the Syrian kingdom. These two armies had laid siege to Jerusalem. The Bible relates that the House of David and King Ahaz were gripped with fear. In response these two warring armies, God sent the prophet Isaiah to reassure King Ahaz that divine protection was at hand -- the Almighty would protect him, their deliverance was assured, and these two hostile armies would fail in their attempt to subjugate Jerusalem.
It is clear from this chapter that Isaiah's declaration was a prophecy of the unsuccessful siege of Jerusalem by the two armies of the Kingdoms of Israel and Syria, not a virgin birth more than 700 years later. If we interpret this chapter as referring to Jesus' birth, what possible comfort and assurance would Ahaz, who was surrounded by two overwhelming military enemies, have found in the birth of a child seven centuries later? Both he and his people would be long dead and buried. Such a sign would make no sense.
For Matthew, the prophet's original intent regarding the young woman in Isaiah 7:14 was entirely superseded by his fervid desire to somehow prove to the Jewish people that the virgin birth was prophesied in the Hebrew scriptures. Bear in mind that the author of the first Gospel -- more than any other writer in the New Testament -- shaped and contoured his treatise with the deliberate purpose of promoting Christianity among the Jews. In essence, Matthew was writing with a Jewish audience in mind. He understood that in order to convince the Jewish people to embrace Jesus as the messiah, it was essential to demonstrate his claim of the virgin birth from the Jewish scriptures. Luke, in contrast, was writing for a non-Jewish, Greek audience and therefore makes no attempt to support his version of the virgin birth from the Hebrew Bible.
In his attempt to promote numerous Christian creeds among the Jews, Matthew was faced with a serious quandary. How would he prove that Jesus was the messiah from the Jewish scriptures when there is no relationship between the Jesus of Nazareth of the New Testament and the messianic prophecies of the Jewish scriptures? How was he going to merge newly inculcated pagan myths, such as the virgin birth, into Christianity with a Hebrew Bible in which a belief in a virgin birth was unknown?
In order to accomplish this daunting task, verses in the Hebrew scriptures were altered, misquoted, taken out of context, and mistranslated by the author of the Book of Matthew in order to make Jesus' life fit traditional Jewish messianic parameters, and to make traditional Jewish messianic parameters fit the life of Jesus. In essence, he had to claim that it was the Hebrew prophets themselves who foretold that Jesus was the messiah. It is therefore no coincidence that no other writer in the New Testament misuses the Jewish scriptures with abandon to the extent that Matthew does throughout his Gospel.
Now a discussion of ?almah? itself. The masculine root of almah is elem ("???") meaning "youth" or "young man of the age of puberty". Feminizing these terms would result in "young woman" or "young woman of the age of puberty", but the actual definition is: "girl of marriageable age". This sense of the word continues to the modern Hebrew where almah still means "damsel" (a young woman or girl) and "miss" (a young or unmarried woman). It does not denote a virgin or sexual purity but age. A different Hebrew word, bethulah ("?????"), is most commonly used for virgin. Other uses of ?almah? in the Bible further clarify this. For example, the word is used in Exodus 2:8 to refer to the older sister of Moses. In Psalms 68:25/26, referring to a victory parade, the participants are listed in order of appearance: 1) the singers; 2) the musicians; and 3) the "alamot" playing cymbals or tambourines. Certainly ?virgins? is not indicated here. In Song of Songs 1:3, the declaration about the man is made that all the alamot adore him. Again, most likely ?young maidens? rather than ?virgins?. Finally, in the passage, the Hebrew when properly translated read, ?THE young woman? and **not** ?A young woman?. This likely points to someone whom Isaiah knew--this is a present-time, **not** future-looking statement.