Luke 2:10-12

But the angel said to them, "Do not be afraid; for see - I am bringing you good news of great joy for all the people: to you is born this day in the city of David a Savior, who is the Messiah, the Lord.  This will be a sign for you: you will find a child wrapped in bands of cloth and lying in a manger."

The sign of "Christ the Lord's" coming is unusual to say the least: a newborn in a feed trough!  The audience to whom this message is addressed is equally odd:  shepherds; people of no standing in the community.  They are the no-accounts.  It is to the nobodies that the angels bring greetings of good news.  The heavenly host, the army of God, appears to praise God as well.  This history-shattering event that brings glory to heaven brings peace to earth.  Heaven and earth share in the joy of this birth.