O Emmanuel

Icon of the Blessed Virgin Mary holding the child Immanuel (16th cent. St. Catherine's Monastery, Mount Sinai).

The Latin antiphon is:

O Emmanuel, Rex et legifer noster,

exspectatio Gentium, et Salvator earum:

veni ad salvandum nos, Domine, Deus noster.

or in English:

O Emmanuel, our king and our lawgiver,

the hope of the nations and their Saviour:

Come and save us, O Lord our God.

It's based on one of the most familiar of the Advent/Christmas readings:

"Therefore 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." Isaiah 7:14

God is with us which is a scary and comforting thought.  Scary because it means the Holy of Holies is among us, dwelling in an earthly tabernacle of frail flesh.  Comforting because it means that God utterly identifies with us - adopts us - and grants us the Kingdom as a gift.  Great, eh?