Judah was at war with Israel and Syria. The existence of the Jewish nation state was tenuous. Would they survive? Would they be wiped out? Ahaz didn’t know. He didn’t want to be destroyed.
So Isaiah came to tell him Judah would not be wiped out. He even told Ahaz to ask for a sign for proof. But Ahaz was too proud to ask God to give Him a promise. He thought it silly. He tried to look pious, but really He did it in unbelief, because He didn’t believe God.
God gave him the sign anyway. A Virgin will conceive and give birth to a Son and call His Name Immanuel. A Virgin, descended from David, espoused to Ahaz’s own heir hundreds of years later, would give birth to David’s Son, The King of Israel, The Good Shepherd of God’s faithful people.
What issues, what wars, do you have in your life? This Child is come to rescue you from them. He is proof that God will be with you and help you. He’s your sign that glory comes after pain. Glory does not come in this life; after all, He was glorified only after He died and when He rose. So your glory is sure to come, not now, but after you die and when you rise.
He is Immanuel. He is God with us. God took on our flesh. He dwelt among us. He is ascended into heaven, but He still dwells among us. He promises to be with us always, even to the end of the age? How? You are baptized into His Name. You bear His Name. Where His Name is, there He is, protecting and guiding and saving you. You receive His Body and drink His Blood at His Altar, believing His Word. He dwells in you and you in Him.