This verse pinpoints Isaiah’s primary intention as communicating an immediate reality for Ahaz. Before this child is old enough to differentiate good from evil, Assyria will invade. Although directed at the Syrian-Israel coalition, the invasion will also have dire consequences for Judah. Ludlow fills in the historic picture:
The fulfillment came about in successive stages. First, Tiglath-Pileser III (Pul) attacked Syria and Israel in 732 B.C. and took many Israelites captive to Assyria, especially those from the northern tribes. Secondly, in 730–727, Pul annexed the Transjordan area and deported large numbers of the Israelite tribes from that area to the far reaches of the Assyrian Empire. Third, in 726, Hoshea refused to pay Assyrian tribute, and Pul’s successor, Shalmaneser, retaliated by attacking Israel and besieging Samaria, which fell in 722 B.C. Thus, within a dozen years of Isaiah’s prophecy, the alliance had completely failed, and three major groups of Israelites had been deported. Finally, large groups of the Israelites fled from Assyria to the remote areas northward and became the lost Ten Tribes of Israel. Apparently, within about fifty years of their leaving Assyria, they were scattered so widely that many of them no longer existed as a cohesive group. Thereby Isaiah’s prophecy to Ephraim was completely realized.
In the last part of the prophecy, Isaiah warns Judah that she must remain firm in her trust of the Lord or she will not be able to stand. Unfortunately, Ahaz did not heed this warning and relied instead upon the Assyrians for deliverance. The Assyrians did hinder the Syro-Israelite attack by destroying Syria and large parts of Israel, but since the Assyrians desired more territory and wealth, Judah found herself paying tribute to avoid war.
The “sign,” therefore, refers to Israel’s destruction by Assyria, which will happen in so brief a time that a newborn will not have grown enough to learn good from evil. This sign must also be fulfilled soon enough after the prophecy that Ahaz could recognize it.
What then of the virgin and the Messianic name? The mother and her son are mechanisms in the sign, not the sign themselves. Reading “young woman” rather than “virgin” contextualizes the mother as a generic mother rather than a specific one. The name “God with us” just as easily connotes the fulfillment of the sign as it declares the Atoning Messiah’s birth. In the historical context of Ahaz’s reign, both mother and son are irrelevant. We need not search for any special woman or an ominously named child. They are meant to be generic—the medium for explaining a time period before the destruction of Israel (an event that Ahaz will live to witness) and the subject of the previous prophetic statements from Isaiah. Indeed, the Isaiah’s next verses strongly echo the themes and language of prophecies that refer to Israel’s destruction.
Ludlow would disagree, preferring to see the mother and son as real people in that timeframe. After discussing the scholarly debate on the issue, he notes: “Instead of the son of any woman fulfilling the promise, the son of one particular woman was designated. In the Hebrew, a definite article precedes the term translated as ‘virgin’ or ‘young woman,’ indicating that she is the virgin not just a virgin or any young woman.”
However, he does agree that, “regardless of the precise identity of the woman and her child, it appears obvious that the circumstances of the child’s birth and the conditions surrounding his early life were so much an evidence of divine protection as to make proper his name, Immanuel, for God was truly with the people of Judah.”