The prophet Isaiah had a difficult assignment. Called to reprove the kingdom of Judah in the eighth century BC, he knew that most people would not be receptive to the correction he offered. Even so, he faithfully warned of coming judgment while giving reasons for hope (Isa 6:9-13).
Hard times lay ahead for Judah, but God would not abandon his people.
We see Isaiah's mission and message at work in the seventh chapter. Early in the reign of King Ahaz (c. 735 BC), Jerusalem faced a serious military threat from the combined forces of Syria and the northern kingdom of Israel (vv. 1-2). Israel and Syria had formed an alliance against the powerful Assyrians, and they wanted to force Judah to join them. If Ahaz would not cooperate with them, they planned to replace him with someone who would (vv. 5-6).
In the face of this threat, God sent Isaiah to encourage young Ahaz to trust in him. Rezin and Pekah, the kings of Syria and Israel, were mere human beings whose schemes would be fruitless. On the other hand, the Creator and King of the Universe stood behind the throne of David (vv. 3-9; see 2 Sa 7).
As an incentive to faith, Ahaz was directed to ask God for a sign, with no limitation placed on his request (vv. 10-11). Sadly, Ahaz declined this generous offer, making the excuse that he did not want to put God to the test (v. 12). He may have already decided by that point to place his trust in an alliance with Assyria (2 Ki 16:5-7).
Since Ahaz was not receptive to God's instruction, Isaiah responded with a message to the whole house of David, the descendants of David in that generation and thereafter. Ahaz had refused to ask God for a sign, but God would give them a sign: Behold, the virgin shall conceive and bear a son, and shall call his name Immanuel (v. 14).
Isaiah went on to speak about the future of the house of David and the kingdom of Judah (vv. 15-25). In the short term, the enemies Ahaz feared would soon be defeated (v. 16). In the longer term, Judah's trust in the Assyrians would backfire, and God would use Assyria to punish Israel and Judah. (These things did indeed come to pass.)
Through it all, God would be with his people as implied by the name Immanuel (God with us).
Verse 16 says that Ahaz's enemies would be defeated before the boy knows how to refuse the evil and choose the good. If the boy in this verse is Immanuel, then the sign began with the birth of a son—perhaps Ahaz's son, Hezekiah—shortly after Isaiah spoke. Or, the boy could be Isaiah's son, Shear-jashub, who accompanied his father to speak to Ahaz. If so, verse 16 is an aside intended specifically for Ahaz. (In verse 16, "you" is singular rather than plural as in the rest of the prophecy.) (1)
In any case, there are indications that the main manifestation of the Immanuel sign would come later. The child's mother is referred to as the virgin, a specially chosen maiden. Since the sign offered to Ahaz could be as deep as Sheol or high as heaven (v. 11), we would expect the sign of verse 14 to be momentous. Because there are predictions of a great Davidic king in Isaiah 9:6-7 and Isaiah 11, it is reasonable to conclude that Isaiah 7:14 is also a messianic prophecy.
Moreover, the mention of curds and honey in verse 15 connects Immanuel with a later time when Israel would suffer under foreign domination (see vv. 17-25). Often, we associate milk and honey with the abundance of the Promised Land. But in this context, curds and honey refers to a limited diet available when the land has been ravaged by enemies and is uncultivated, growing briers and thorns (vv, 23-24). Isaiah's prophecy pictures a coming time of punishment and purification for Judah, and verse 15 suggests that Immanuel would be born during such an era.
With the benefit of hindsight and the guidance of the Holy Spirit, we Christians see Jesus clearly in the sign of Immanuel.
Verse 15 says that Immanuel would eat curds and honey when he knows how to refuse the evil and choose the good. This phrase may refer to more than the boy reaching an age of accountability. It can also be rendered so that he may know how to refuse the evil and choose the good, as in the Vulgate translation. (2)
This rendering of verse 15 reminds us of the Israelites being fed a limited diet in the wilderness in order to learn obedience (Dt 8:3). Whereas Israel often failed to refuse the evil and choose the good, Jesus resisted temptation (Mt 4), carried out his mission to die for the sins of the world, and learned obedience through what he suffered (Heb 5:8). He is the Wonderful Counselor who judges righteously (Isa 9:6; 11:3-5).
Christian reflection on the Immanuel prophecy began with the apostles, who recognized the Virgin Birth and Incarnation in the words of Isaiah 7:14 (see Mt 1:22-23). The sign of Immanuel truly is as deep as Sheol or high as heaven. It is a sign to Israel and the nations of the amazing, incomprehensible love and faithfulness of God the Father and Jesus the Messiah.
(1) See, for example, Michael Rydelnik, The Messianic Hope, B&H Publishing Group, Nashville, 2010, chapter 10.
(2) See Joseph Jensen, The Age of Immanuel, Catholic Biblical Quarterly 41 (1979) 220-239.