Isaiah 7:1 Now it came about in the days of Ahaz, the son of Jotham, the son of Uzziah, king of Judah, that Rezin the king of Aram and Pekah the son of Remaliah, king of Israel, went up to Jerusalem to wage war against it, but could not [a]conquer it. 2 When it was reported to the house of David, saying, The Arameans [b]have camped in Ephraim, his heart and the hearts of his people shook as the trees of the forest shake [c]with the wind.Obviously the prophesy got the name wrong, but explanations for that are a dime a dozen. And the word used for virgin can indicate any young woman (and in any case virgins can can pregnant without any help from God!).
3 Then the Lord said to Isaiah, Go out now to meet Ahaz, you and your son [d]Shear-jashub, at the end of the conduit of the upper pool, on the highway to the [e]fullers field, 4 and say to him, Take care and be calm, have no fear and do not be fainthearted because of these two stubs of smoldering firebrands, on account of the fierce anger of Rezin and Aram and the son of Remaliah. 5 Because Aram, with Ephraim and the son of Remaliah, has planned evil against you, saying, 6 Let us go up against Judah and [f]terrorize it, and make for ourselves a breach in [g]its walls and set up the son of Tabeel as king in the midst of it, 7 thus says the Lord [h]God: It shall not stand nor shall it come to pass. 8 For the head of Aram is Damascus and the head of Damascus is Rezin (now within another 65 years Ephraim will be shattered, so that it is no longer a people), 9 and the head of Ephraim is Samaria and the head of Samaria is the son of Remaliah. If you will not believe, you surely shall not [i]last.
10 Then the Lord spoke again to Ahaz, saying, 11 Ask a sign for yourself from the Lord your God; [j]make it deep as Sheol or high as [k]heaven. 12 But Ahaz said, I will not ask, nor will I test the Lord! 13 Then he said, Listen now, O house of David! Is it too slight a thing for you to try the patience of men, that you will try the patience of my God as well? 14 Therefore the Lord Himself will give you a sign: Behold, a [l]virgin will be with child and bear a son, and she will call His name [m]Immanuel. 15 He will eat curds and honey [n]at the time He knows enough to refuse evil and choose good. 16 For before the boy will know enough to refuse evil and choose good, the land whose two kings you dread will be forsaken.
What is more interesting is the context. The nation of Judah was ruled by King Ahaz from Jerusalem, and was threatened by two enemies, Israel (aka Ephraim) and Syria (aka Aram aka Damascus). God has Isaiah tell the king that all will be okay. God then gives a sign to reassure Ahaz: A boy will be born to a young woman, and before that boy has learnt to choose good (i.e., just a few years), the two enemies of Judah will have fallen.
If the author of Matthew is to be believed, this boy was born some 700 years later. If we believe Matthew, then God's reassurance to the king is: Don't worry Ahaz, within 700 years the two nations you fear so much will have fallen.
Which is no reassurance at all!
Israel and Syria did indeed fall, soon after the prophesy supposedly made, to Assyria, from whose control they had just rebelled. The "prophecy" was written a generation later as a warning to Ahaz's son, Hezekiah, advising him not to join other nations rebelling against the Assyrian overlords (advise that was unfortunately ignored).
This supposed prophecy has nothing to do with Jesus; it was made and fulfilled centuiries before. Nevertheless, the author of the Gospel of Matthew pretended it was about Jesus to support his own agenda, and to this day Christians will cite this text as vindicating their belief in Jesus.