“Therefore the Lord himself will give you a sign: The virgin will conceive and give birth to a son, and will call him Immanuel.”
Isaiah, reputed to Isaiah Ben Amos of the 8th century, but thought to be more than a few writers, is often called the fifth Gospel. It is lyrical and words of Isaiah are found in the libretto of Handel's Messiah, and expressions such as 'Swords into plough shares' and 'Voice in the wilderness.'
This verse is often misunderstood by Christians. Isaiah is warning king Hezekiah of what will happen to any who do not keep to God's law. But the verse was revised at a later date to say King Ahaz and reflect an earlier time. It is said Hezekiah had been unwilling to test the prophecy, as that would be challenging God. The sign Isaiah offered to Hezekiah was not looked for, but found fruit several hundred years later.