God tells Judah not to fear when Syria and Israel ally against them. They will both fall soon.
God invites King Ahaz to ask for a sign of this, but he refuses with some religious excuse.
So God gives him a sign anyway: the virgin will have a child named Immanuel, and before he knows good from evil Israel and Syria will be gone. Egypt and Assyria will come in and the land will be briers to hunt and pasture in, instead of cultivated farmland.
God has Isaiah name his son "quick to the spoil, hurry to the plunder." Since Judah has refused God He will bring Assyria to conquer them.
Lots of trouble and disobedience and darkness is coming, but don't think it's all a conspiracy. Take refuge in God, and keep teaching the Word of God.
How this is about Jesus
The famous Isaiah 7:14 prophecy of Immanuel is a microcosm of redemptive history. Short term defeat for God's people (Judah by Israel in Isaiah's day, Israel by Rome in Jesus' day), but a remnant survives to spiritually overcome their conquerors (conversion of much of Roman Empire).
8 - In Hebrews 2:13, we see verse 17-18 applied to Jesus. He stands before God with us, trusting God will save us.
7 - It's interesting God gives this assuring sign, when in the short term Israel DID conquer Judah (2 Chronicles 28). God continues in His purpose to save His people, even when met with stubborn unbelief by the rulers of His people. What a relief, as we see stubborn unbelief in our rulers today!
8 - when darkness and spiritual lost-ness increases in a culture, as it is today, verses 12-20 are especially important for Christians. We take refuge in God, by returning to His Word.
Isaiah 8:16-17, 20
"Bind up the testimony; seal the teaching[p] among my disciples. 17 I will wait for the Lord, who is hiding his face from the house of Jacob, and I will hope in him.... To the teaching and to the testimony!"