Many people need some sort of sign to give them hope and encouragement. King Ahaz was terrified of the enemy that was besieging Jerusalem. Isaiah offered him a sign but at first Ahaz refused - he did not want to test God. Isaiah gave him one anyway: a young woman will conceive, and the child's name would be Emmanuel - God is with us. This was intended to happen immediately, within the lifetime of Ahaz. It was a meaningful message for him, and Jerusalem was saved.

Centuries later, the evangelists saw the birth of Jesus as a fulfillment of that prophecy. Although it had already been fulfilled once, this was sort of a 'second life' for the prophecy. The angel's annunciation was a sign that God was still at work, guiding and protecting Israel. Although Mary did not really understand what was happening, she was assured that it was the hand of God. That was enough for her - she told the angel that it should be done to her according to God's will. God accomplishes great things when people are humble and open, willing to be used as God's instrument. Let us always live in expectation that God is going to do great and wonderful things.