“Again the LORD spoke to Ahaz, “Ask a sign of the LORD your God; let it be deep as Sheol or high as heaven.” But Ahaz said, “I will not ask, and I will not put the LORD to the test.” And he said, “Hear then, O house of David! Is it too little for you to weary men, that you weary my God also? Therefore the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel. He shall eat curds and honey when he knows how to refuse the evil and choose the good. For before the boy knows how to refuse the evil and choose the good, the land whose two kings you dread will be deserted. The LORD will bring upon you and upon your people and upon your father's house such days as have not come since the day that Ephraim departed from Judah—the king of Assyria.” (Isaiah 7:10-17)
Ahaz was asked to request a sign, but in his unbelief refuses to do so. Isaiah in his rebuke of Ahaz announces the Lord will “give you (in context referring to Ahaz) a sign.” A time frame is given which is a critical part of the sign to Ahaz. A child will be born, and by the time the child attains a certain age of discernment Syria and Israel will be no more. Commentators debate what that age is, but none will say it is more than the age of 12. Both the child and the child’s age are critical components of the sign to Ahaz. The name Immanuel (God with us) was a sign to Ahaz that God had not abandoned His people. God’s purposes for His people would be accomplished in spite of Ahaz’s unbelief.
As Leupold observes, “The major difficulty happens to be that a contemporary person is almost demanded by the very situation involved… At the same time a contemporary child seems to be inexorably demanded by the passage.” (Exposition of Isaiah, H.C. Leupold)
Then we come to the Gospel of Matthew where this prophecy of Immanuel is cited:
“Now the birth of Jesus Christ took place in this way. When his mother Mary had been betrothed to Joseph, before they came together she was found to be with child from the Holy Spirit. And her husband Joseph, being a just man and unwilling to put her to shame, resolved to divorce her quietly. But as he considered these things, behold, an angel of the Lord appeared to him in a dream, saying, “Joseph, son of David, do not fear to take Mary as your wife, for that which is conceived in her is from the Holy Spirit. She will bear a son, and you shall call his name Jesus, for he will save his people from their sins.” All this took place to fulfill what the Lord had spoken by the prophet: “Behold, the virgin shall conceive and bear a son, and they shall call his name Immanuel” (which means, God with us). When Joseph woke from sleep, he did as the angel of the Lord commanded him: he took his wife, but knew her not until she had given birth to a son. And he called his name Jesus.” (Matthew 1:18-25)
Leupold holds the view that the fulfillment of the Isaiah 7 prophecy was delayed until the time Matthew speaks of. I find that explanation unsatisfactory and problematic. For the matter prophesied to be a sign to Ahaz, there had to be some kind of fulfillment in Ahaz’s lifetime. The birth of Isaiah's child, Maher-shalal-baz, in the immediate succeeding context of Isaiah 8:1-3 seems the best understanding of the immediate fulfillment of the sign prophecy to Ahaz in chapter 7.
How then are we to understand Matthew’s use of the Isaiah 7 prophecy of Immanuel?
The best understanding of Matthew’s reference is that the woman who at the time of the prophecy was an unmarried virgin and then became Isaiah’s wife and bore him the son spoken of in chapter 8, is a type or foreshadowing of the Virgin Mary. Likewise the child of Isaiah 8:1-3 was a type of or foreshadowing of the Messiah Jesus. This is in essence, the view of the following commentators:
"Language is selected such as, while partially applicable to the immediate event, receives its fullest, most appropriate, and exhaustive accomplishment in Messianic events. The New Testament application of such prophecies is not a strained “accommodation”; rather the temporary fulfilment of an adaptation of the far-reaching prophecy to the present passing event, which foreshadows typically the great central end of prophecy, Jesus Christ (Rev 19:10). Evidently the wording is such as to apply more fully to Jesus Christ than to the prophet’s son; “virgin” applies, in its simplest sense, to the Virgin Mary, rather than to the prophetess who ceased to be a virgin when she “conceived”; “Immanuel,” God with us (Jn 1:14; Rev 21:3), cannot in a strict sense apply to Isaiah’s son, but only to Him who is presently called expressly (Is 9:6), “the Child, the Son, Wonderful (compare Is 8:18), the mighty God.” Local and temporary features (as in Is 7:15, 16) are added in every type; otherwise it would be no type, but the thing itself. There are resemblances to the great Antitype sufficient to be recognized by those who seek them; dissimilarities enough to confound those who do not desire to discover them." (Jamieson, Fausset, & Brown, “Commentary Critical and Explanatory on the Whole Bible”)
“A virgin shall conceive. The word for virgin here is carefully chosen. Etymologically ‘almậ does not necessarily signify a virgo intacta (an untouched maiden). In actual usage in the Hebrew Scriptures, however, it refers only to a maiden chaste and unmarried (so far as the context shows). This well fits the prospective mother alluded to in this situation. Judging from 8:1-4, the typical mother was the prophetess who became Isaiah’s wife within a short time after this prophecy was spoken. Therefore she was a virgin at the time this promise was given. She serves as a type of the Virgin Mary, who remained a virgin even after her miraculous conception by the Holy Spirit. The son of this prophetess, correspondingly, is a type of the Messianic Immanuel as shortly will be explained.” (Wycliffe Bible Commentary, Isaiah contribution by Gleason L. Archer Jr.)
This view of type and fulfillment best satisfies the demand for an immediate fulfillment in the time of Isaiah and Ahaz, and allowing for an understanding of Jesus Christ being the fullness of what is meant by the name Immanuel per Matthew’s citation. This is what is pointed to by the more direct prophecy in Isaiah 9:6-7:
“For to us a child is born, to us a son is given; and the government shall be upon his shoulder, and his name shall be called Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace. Of the increase of his government and of peace there will be no end, on the throne of David and over his kingdom, to establish it and to uphold it with justice and with righteousness from this time forth and forevermore. The zeal of the LORD of hosts will do this.”