This is a brief but timely post on Matthew's use of Isaiah 7:14 in the first chapter of his Gospel (1:23). I have posted on this topic before (here, here, and here).
It is often the case that Matthew's use of Isaiah in this passage is interpreted as Matthew's attempt to prove that the Virgin Birth had been predicted in the Old Testament. A very helpful recent post (see also the helpful comments) by T.M. Law takes this line. Also, on the OUP blog Daniel Harrington has a post on the infancy narratives in Matthew and Luke. He also seems to assume that Matthew's point in quoting Isa. was to establish that Jesus fulfills the prediction of a virgin birth. At one point, he says:
Next, he explains how the virginal conception of Jesus through the Holy Spirit fulfilled Isaiah’s prophecy (7:14) [...].I wanted to reiterate here--as I have done in this post-that I'm not convinced that this is the correct interpretation of Matthew's intentions. Rather than using Isaiah's prophecy as a prediction of the Virgin Birth, I think it probably makes better sense to interpret Matthew as using Isaiah's prophecy as a prediction of the advent of the Immanuel child, "which translated means God With Us" (1:23).
I wouldn't deny that Matthew also sees in Isaiah a prediction of a Virgin Birth--and John Meade's comments, at T.M. Law's post linked above, regarding the different translations between the LXX and the three later Jewish translators need to be factored into the discussion. But I take it as obvious that the part of the prophecy highlighted by Matthew himself is the name of the child--he is truly God With Us. The fact that the child was conceived by the Holy Spirit (1:20) also shows the Immanuel has finally arrived!