Matthew 1:23

a virgin shall be with child Properly, according to the Greek text and to the original Hebrew, " The virgin shall be with child, and shall bring forth a son, and they (Hebr. she) shall call his name God with us;" see Isaiah 7:14. The historical crisis was this, Ahaz is alarmed by the threatened invasion of Pekah and Rezin the confederate kings of Samaria and Damascus. Isaiah reassures Ahaz, who hypocritically refuses to ask for a sign. Yet a sign is given. She, who is now unmarried, shall bear a son, probably a scion of the royal house of David; he shall be called Emmanuel, and before he arrives at years of discretion the deliverance shall come, though a heavier distress is at hand.

The prophecy is distinctly Messianic, but the sign in Isaiah is not concerned with the mannerof the child's birth, but with the name and the deliverance which should happen in his infancy. Therefore, the weight of the reference is to the name "Emmanuel" and to the true Son of David, whose birth was the sign of His people's deliverance.