JESUS, and the Sign (Is.7)

In chapter 7 of Isaiah, we have a double prophecy.  The sign that God gave to king Ahaz applied to both the present time (back then) as well as the future...

(Isaiah 7:10-14)  Then the Lord spoke again to Ahaz, saying, 11 “Ask a sign for yourself from the Lord your God; make it deep as Sheol or high as 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 virgin will be with child and bear a son, and she will call His name Immanuel..."

It is true that we should never test God, but Ahaz made that statement thinking he would just sound pious enough to trick God, since Ahaz was actually going to make Syria an alliance (trusting in man's power and not God's power).  Therefore God gave Ahaz a unique sign, so that when that happened along side the devastation of Israel - he'd see God's power and realize he should have trusted God instead.  What happened back then (just before Israel's devastation) was - Isaiah's first wife died after giving birth to a child, so he remarried and his young bride then had a baby to raise.

Just like the sinfulness of Ahaz needed addressing, all mankind are sinners and need a Savior to be their Light to follow.  Therefore what it meant later (in the future for Ahaz and Isarel, etc.)  was literal:

(Matthew 1:18-23)  Now the birth of Jesus [r]Christ was as follows: when His mother Mary had been betrothed to Joseph, before they came together she was found to be with child by the Holy Spirit. 19 And Joseph her husband, being a righteous man and not wanting to disgrace her, planned to send her away secretly. 20 But when he had considered this, 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 the Child who has been conceived in her is of the Holy Spirit. 21 She will bear a Son; and you shall call His name Jesus, for He will save His people from their sins.” 22 Now all this took place to fulfill what was spoken by the Lord through the prophet: 23 “Behold, the virgin shall be with child and shall bear a Son, and they shall call His name Immanuel,” which translated means, “God with us.”

A virgin birth was critical to authentically give the 100% human aspect to Jesus, as well as to be born into king David's lineage.  And to be of the Holy Spirit was critical to authentically demonstrate that Jesus is 100% God.  Jesus came with the specific purpose to provide salvation.

(Galatians 4:4-5)  But when the fullness of the time came, God sent forth His Son, born of a woman, born under the Law, 5 so that He might redeem those who were under the Law, that we might receive the adoption as sons.