Judah was in desperate straits. The strength and prosperity of King Uzziah had given way to the weakness and poverty of King Ahaz. Tilgath Pileser III, the ascendant ruler of Assyria, was expanding with a mighty army and his neighbors, Syria and Israel, had attacked Judah to force it to ally with them against Assyria. Judah had suffered a severe defeat, and at that moment, Ahaz was not thinking about something that was going to happen 730 years later. Probably, Isaiah wasn’t either. Therefore the child promised in Isaiah 7:14 was not, at least in Ahaz’ mind, the future Messiah. Isaiah had promised him a sign that God would deliver him and his nation from the combined might of Israel and Syria and the child was to be the sign. The sign was not that a young woman would bear a child; this is an ordinary part of human experience. Rather it was that the birth of this child would begin the countdown to destruction for Judah’s enemies. Specifically, the kings that Ahaz feared would be destroyed before the child reached preadolescence.
That prophecy was most likely fulfilled by the birth of Isaiah’s second son, Maher-shalal-hashbaz (MSH). According to Herbert M .Wolf, “almah” most reasonably refers to a young woman of marriageable age, who in Hebrew culture was expected to be a virgin. The event in 8:1-2 is likely the marriage ceremony between Isaiah and his new wife, and the child is conceived in verse 3. Isaiah’s prophetess was a virgin when she married but obviously not a virgin when she conceived. In verse 4, Isaiah clarified his prophecy; this time saying that before his son was even old enough to talk, Israel and Syria would be no more. Thus MSH was the immediate fulfillment of the prophecy in Isaiah 7:14.
Richard Niessen also went into some detail about the meaning of “almah” in 7:14. The roots of the term are “to conceal” and “to be strong, or sexually mature”. “To conceal” is in contrast to “to uncover”, and the euphemism for sexual sin in Hebrew is to “uncover nakedness”. In Genesis 24:43 the term is used of Rebekah and the passage clearly spells out that she was a virgin. In Exodus 2:4 the term is used of Miriam, suggesting that she was a child still in her mother’s household and therefore clearly a virgin as well. In Psalm 68:25 “almah” described young women leading a dance of worship into the sanctuary. These women were usually unmarried and therefore expected to be virgins. Proverbs 30:19 is commonly seen as referring to adultery (compared to 30:20) and therefore would exclude virginity by definition. However, the parallelism with the other portions of verse 19 is better explained if the text referred to an unmarried man wooing a virgin in the hopes of marrying her. In Song of Solomon 1:3 “almah” refers to maidens as yet without a husband and in Song of Solomon 6:8 it speaks of unmarried women who would eventually enter the king’s harem. Therefore they had to be virgins. In sum, “almah” refers to virgins, women who have never had sex, in every instance. The other words commonly translated “young woman” do not have the same connotation.
The child in view in Isaiah 7:14 was MSH, but at the same time, Matthew applied Isaiah 7:14 to the birth of Jesus (1:23). Since Scripture is without error and Matthew applied that verse to Jesus, we must do so as well. When interpreting the Old Testament, modern exegetes must look for an immediate fulfillment of prophecy during the times of the prophet and his people. We must also seek another, later and greater fulfillment. Such appears to be the case here.
Richard Niessen, The Virginity of the עלמה `almah in Isaiah 7:14, Bibliotheca Sacra – April – June 1980, 133-150
Herbert M Wolf, A Solution to the Immanuel Prophecy in Isaiah 7:14-8:22, Journal of Biblical Literature, vol 91, no 4 (Dec 1972), pp 449-456