20 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 be afraid to take Mary as your wife; for that which is conceived in her is from (the) Holy Spirit.
21 She will bear a son, and you will call his name Jesus; for he will save his people from their sins.
22 All this took place that what was spoken by the Lord through the prophet might be fulfilled, saying,
23 ‘Behold, the young woman shall have in belly and will bear a son, and they shall call his name Emmanuel, which is interpreted “God with us”.’
Conceived by the Holy Spirit
The Christmas stories have to do more with Jesus as Messiah than with the incarnation. There is no suggestion that only in this way could he be sinless, etc.; it is not taken as an argument for Jesus’ divinity. Rather the virgin birth is a ‘sign’ to Joseph (the reference to the prophecy occurs in the middle of the account of Joseph’s dream) of God’s involvement, just as the birth of the child in Is.7:14 is a sign to Ahaz of God’s presence with Israel.
It is not even clear that Matthew saw any great biological significance in the term parthenos; arguably it is the fact that she is unmarried (cf. Luke 1:34) that is important (Joseph is concerned about the shame attached to her condition, not about the miraculous nature of the conception), in which case the real point may well be that Jesus was from the beginning an outsider, ‘illegitimate’. Cf. the women listed in the genealogy (Tamar, Rahab, Ruth, Mary) in chapter 1. Mary’s perspective on the situation is rather different (Luke 1:30-35).
None of this necessarily detracts from the miraculous nature of the conception, but it does delimit the theological significance of the event. The idea of incarnation does not require a virgin birth; nor did the story of the virgin birth arise out of belief in the incarnation.
John speaks of an incarnation (‘the word became flesh and dwelt among us’), but the point of reference here is Jesus’ baptism rather than his birth (1:14-15). Moreover, it is not God principally who becomes flesh but the word, life, light (cf. 1 John 1:1-2). If v.9 refers to Israel (cf. 5:43), then the thought is of Jesus as Messiah.
You shall call his name Jesus
The statement corresponds to ‘they will call his name Emmanuel’ in the prophecy. No doubt many pious Jews called their sons ‘Yahweh saves’ in the hope that they would grow up to rescue Israel from oppression.
He will save his people from their sins
This is not a universal statement about salvation; it is restricted to Israel: Jesus will save Israel from the political-religious consequences of its continuing rebellion against YHWH.
Emmanuel, God with us
Perhaps the commonest argument against the truthfulness of this account is that Matthew found this verse in Isaiah, took it out of context, generally misinterpreted it, and fabricated the story of Jesus’ miraculous birth in order to provide a ‘fulfilment’ of the prophecy - proof that Jesus was God incarnate. Now there’s something in this. On the face of it, at least, the child prophesied in Isaiah 7:14 is not the Messiah, he is not the Christ, God’s anointed; and it’s unlikely - though not impossible - that Isaiah thought this child would be conceived supernaturally.
At the time (about 735 BC) Judah was facing attack from the kings of Syria and Israel. Isaiah’s message from the Lord to king Ahaz was that a child would soon be born to a young woman, and that he would be called Immanuel. This was a sign to Ahaz that God would not abandon his people to defeat, because before this child was old enough to distinguish between good and evil - in other words, within a few years - the two kings who now threatened Israel would themselves be defeated. The prophecy proved to be accurate: the Assyrians destroyed Damascus in 732 and Samaria, the capital of the northern kingdom of Israel, ten years later.
So Isaiah wasn’t strictly prophesying the birth of Jesus here. The child doesn’t do anything - he is merely a passive sign of God’s intervention. But in the next chapter Isaiah speaks of the birth of another boy - a son born to Isaiah himself this time by ‘the prophetess’ (v.3). This boy, too, is given a significant name, Maher-Shalal-Hash-Baz, which means ‘quick to the plunder, swift to the spoil’ (v.4). The Lord explains to Isaiah: “Before the boy knows how to say ‘My father’ or ‘My mother,’ the wealth of Damascus and the plunder of Samaria will be carried off by the king of Assyria.”
In effect, this is a repetition of the prophecy about the boy called Immanuel. Then in v.18 Isaiah writes something rather curious: ‘Here am I, and the children the LORD has given me. We are signs and symbols in Israel from the LORD Almighty, who dwells on Mount Zion.’
The identity of these two boys is unimportant - they may even have been the same child. But they are signs from the Lord Almighty. What is interesting is that in the next four chapters Isaiah describes the future salvation of Israel in terms which take us well beyond the immediate historical circumstances of Ahaz’s reign and which are very familiar to us from the Christmas service: ‘The people walking in darkness have seen a great light; on those living in the land of the shadow of death a light has dawned.’ (Is. 9:2)
Most importantly, this salvation hinges on the birth of a child: ‘For to us a child is born, to us a son is given, and the government will be on his shoulders’ (Is. 9:6). The name of this child is also highly significant, for he will be called: ‘Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace’. But this is no mere sign: this is one who will ‘reign on David’s throne and over his kingdom, establishing and upholding it with justice and righteousness from that time on and forever’ (Is. 9:7).
Three references to the birth of a child, each child given a highly significant name - and it becomes very difficult to avoid the impression that Isaiah regarded the child born to the young woman, the child who was to be called Immanuel, who was not himself the Messiah, as a sign, nevertheless, of God’s greater salvation at the end of the age.
I would suggest is that in that one verse about a virgin giving birth to a son and calling him Immanuel (the verse functions rather as a hyperlink to a larger text) Matthew sums up the whole of Isaiah’s prophecy of salvation in these chapters. The child born in Ahaz’s reign is a sign or symbol of the child through whom God would eventually bring salvation to all mankind - and Matthew understood this very well.