This text is difficult, because the sign promised to Ahaz is ambiguous. Is it good news or bad news? Perhaps that is the point, for if God comes to be with us (Immanuel = "God with us"), that will always be both good and bad news. Good news, because God always means people well; bad news, because God's presence will always expose human sin.
Immediately prior to the sign, God has promised that the threat against Judah by the northern kingdom Israel, now in league with Syria, will not succeed (735-732 B.C.E.). In a striking verse, Ahaz is told, "If you do not stand firm in faith, you shall not stand firm at all" (7:9).
At that point, God offers Ahaz a sign, and Ahaz refuses it. The response that he will "not put the LORD to the test" is normally seen positively in Scripture (Deuteronomy 6:16; Matthew 4:7), but when God offers the sign freely, as God does here, to refuse it is an act of little faith and disobedience (Malachi 3:10).
God's subsequent giving of the sign anyway seems to have a negative tone, which adds to the ambiguity of the passage. Still, the news is good initially. A child will be born, named Immanuel ("God with us"), and before the child is perhaps two years old, the threat from the north will be gone. But then, greater danger looms: the attacks from Assyria stand on the horizon (vv. 17-25).
Most English translations refer to the mother of the coming child as a "young woman" (properly translating the Hebrew 'almah). Centuries later, however, the Septuagint (Greek translation of the Old Testament) used the word parthenos or "virgin," thus setting up the New Testament's use of the text to refer to Mary's virginal conception of Jesus (Matthew 1:23). This seems to be an example of the book of Isaiah's understanding of the word of God as a living reality, one that endures forever (Isaiah 40:8) and does not return empty, but continues to accomplish God's purpose (55:10-11). The promise had its own meaning in Isaiah's day, but it lives on, and God uses it for a new purpose in a new day.
10 Again the Lord spoke to Ahaz, saying, 11Ask a sign of the Lord your God; let it be deep as Sheol or high as heaven. 12But Ahaz said, I will not ask, and I will not put the Lord to the test. 13Then Isaiah* said: Hear then, O house of David! Is it too little for you to weary mortals, that you weary my God also? 14Therefore the Lord himself will give you a sign. Look, the young woman* is with child and shall bear a son, and shall name him Immanuel.* 15He shall eat curds and honey by the time he knows how to refuse the evil and choose the good. 16For before the child knows how to refuse the evil and choose the good, the land before whose two kings you are in dread will be deserted. 17The Lord will bring on you and on your people and on your ancestral house such days as have not come since the day that Ephraim departed from Judahthe king of Assyria.
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org