Prison, November 21st 1943, Dietrich Bonhoeffer writes his good friend Eberhand Bethge:
“Life in a prison cell may well be compared to Advent; one waits, hopes, and does this, that, or the other–things that are really of no consequence–the door is shut and can be opened only from the outside.”
When Joseph purposes to divorce Mary quietly, the angel visits him via dream to tell him “the child conceived in her is from the Holy Spirit.” The mission of this unforeseen, yet not unhoped for, child is then summarized in the single line of — “She will bear a son and you are to name him Jesus, for he will save his people from their sins.” What the nation Israel, and indeed, though unknown to it as yet, the whole world had long hoped for was coming to pass by a newly expecting young Jewish girl and the birth of a son to be named Jesus. This new-conceived child from the Holy Spirit would be the deliverer of his people.
Yet deliverance from sin means more than individual sinners feeling the inward change of guilt from wrong acts done being washed away. Sin, for Israel and for the world, was much larger. It was sin which had driven Israel to exile eastward in Babylon and which even now had them subjugated to the rule of Rome, and it was sin which had the whole world exiled eastward from Eden, subjugated to the “principalities and powers.” To be saved from sin was more than inward peace, but was freedom from the consequences such sin had wrought. For Israel being saved from sin was to return from exile, to see the war-machine of iron shod Rome vanquished, for the world it was to be loosed from the grip of the powers and seeing all creation headed back to Eden.
This imagery comes into view when we consider the Old Testament passage Matthew cites in the following verses. This Savior-Son-to-be-born is the fulfillment of words taken from the Prophet Isaiah; “Look, the virgin shall conceive and bear a son, and they shall call him Emmanuel.” When read in the larger context of Isaiah we find the setting is that of the political deliverance of Israel. The sign Isaiah’s Emmanuel-Son serves is that “before [he] knows how to refuse the evil and choose the good, the lands before whose two kings [Israel is] in dread will be deserted.” The fulfillment of “God with us,” the meaning of this Emmanuel name, was the rescue of Israel from her enemies. So too the birth of this son of Mary, son of God.
The birth of Jesus signified the presence of Israel’s God with his people; not just in the sense of the incarnation, YHWH made flesh, but in the sense of the saving acts of God being active amongst his people once more. This cannot been seen more clearly then in the Magnificat, the Song of Mary. Echoing imagery from Hannah’s song for a son and a deliverer in First Samuel, Mary’s Song exclaims of “The Mighty One,” “He has shown the strength of his arm… He has helped his servant Israel in remembrance of his mercy.” To look upon the infant child is to see the mercy of God manifest in flesh. He has not forgotten his people, not abandon them to grief, to suffering, to darkness, to sin.
What Christmas remembers and celebrates is the coming of a deliverer. Just as Israel under threat of Assyria in the 7th Century BC, under rule of Rome at Christ’s birth, sin loomed over all humanity. It was a prison door though which there was no escape, a darkness with no light. “God with us” is the presence of one who came not just to produce the experience of an inwardly cleansed conscience but one who came to deliver us out of a hand too strong for us. The incarnation was rescue, from our sins yes, and from the exile our sins have left us in. His coming means that the enemies which crouch at our doorstep are to be deserted, that the powers and principalities will not rule forever.
If Advent is as a prison, where all our attempts at freedom, all the busy work we occupy ourselves with to fill the time can never amount to the opening of the door, then Christmas, the Incarnation, the coming of Emmanuel, is both the beauty of him joining us in the cell and the power of the door being thrust open. The incarnation is the first ray of light cast into the darkened cell beckoning us to see we are soon set free. “God with us” is the evidence that those in exile, long god forsaken, are about to return home, the oppressive armies to be conquered and put to flight. “He will save his people from their sins” is the promise of the end of the imprisonment of humanity. “God with us” is his opening the door from the outside.
 Dietrich Bonhoeffer, “Letters and Papers From Prison.” Dietrich Bonhoeffer Works. Vol. 8. (Minneapolis: Fortress Press. 2010) 188