Point Number 3 : 'A sign was fulfilled ' (Ch.1:22-23)
Matthew presented the individual life of Jesus as a re-enactment of various 'delivery' themed episodes in the national history of Israel. That this 'one for the many' idea was fully understood by Israelites is evidenced by: "When Israel was a child, then I loved him and called my son out of Egypt (Hosea 11:1)
One of the 'delivery' highlights Matthew selected to associate with Jesus was the sign given to King Ahaz by the prophet Isaiah (Is. 7:14).
"Therefore the Lord himself shall give you a sign;
Behold, a young woman shall conceive, and bear a son, and shall call his name Immanuel.
Butter and honey shall he eat, that he may know to refuse the evil and choose the good.
For before the child shall know to refuse the evil and choose the good, the land whose two kings thou abhorrest shall be forsaken." (KJV)
The crucial words, in Hebrew, are "hinneh ha'almah harah veyoledet ben" "behold (hinneh) the young woman (ha'almah) is pregnant (harah) and shall give birth (veyoledet) to a son (ben)".
The child referred to was to be a living 'clock' - a physical reminder that as the child waxed and grew, so would the threat from the 'two kings' wane.
Matthew's aim in quoting this passage from Isaiah, and other equally important passages such as the one from Hosea, was to the end of persuading Israelites that their promised 'anointed' deliverer had been LOCATED.
It was NOT to promote an idea as preposterous and pagan as 'virgin birth'!