10 And the angel said to them, “Do not be afraid, for behold, I bring good news to you of great joy which will be for all the people: 11 that today a Savior, who is Christ the Lord, was born for you in the city of David. 12 And this will be the sign for you: you will find the baby wrapped in strips of cloth and lying in a manger.”Luke 2:10-12
“The Birth of Jesus Considered in It’s Spiritual Meaning”
by Martin Luther
Faith is first, and it is right that we recognize it as the most important in every word of God. It is of no value only to believe that this history is true as it is written; for all sinners, even those condemned believe that. The Scripture, God’s Word, does not teach concerning faith, that it is a natural work, without grace. The right and gracious faith which God demands is, that you firmly believe that Christ is born for you, and that this birth took place for your welfare. The Gospel teaches that Christ was born, and that he did and suffered everything in our behalf, as is here declared by the angel: “Behold, I bring you good tidings of great joy which shall be to all the people; for there is born to you this day a Saviour, who is Christ the Lord.” In these words you clearly see that he is born for us.
He does not simply say, Christ is born, but to you he is born, neither does he say, I bring glad tidings, but to you I bring glad tidings of great joy. Furthermore, this joy was not to remain in Christ, but it shall be to all the people. This faith no condemned or wicked man has, nor can he have it; for the right ground of salvation which unites Christ and the believeing heart is that they have all things in common. But what have they?
Christ has a pure, innocent, and holy birth. Man has an unclean, sinful, condemned birth; as David says, Ps. 51:5, “Behold I was brought forth in iniquity; and in sin did my mother conceive me.” Nothing can help this unholy birth except the pure birth of Christ. But Christ’s birth can not be distributed in a material sense neither would that avail any thing; it is therefore imparted spiritually, through the Word, as the angel says, it is given to all who firmly believe so that no harm will come to them because of their impure birth. This it the way and manner in which we are to be cleansed from the miserable birth we have from Adam. For this purpose Christ willed to be born, that through him we might be born again, as he says John 3:3, that it takes place through faith; as also St. James says in 1:18: “Of his own will he brought us forth by the word of truth, that we should be a kind of first-fruits of his creatures.”
We see here how Christ, as it were, takes our birth from us and absorbs it in his birth, and grants us his, that in it we might become pure and holy, as if it were our own, so that every Christian may rejoice and glory in Christ’s birth as much as if he had himself been born of Mary as was Christ. Whoever does not believe this, or doubts, is no Christian.
O, this is the great joy of which the angel speaks. This is the comfort and exceeding goodness of God that, if a man believes this, he can boast of the treasure that Mary is his rightful mother, Christ his brother, and God his father. For these things actually occured and are true, but we must believe. This is the principal thing and the principal treasure in every Gospel, before any doctrine of good works can be taken out of it. Christ must above all things become our own and we become his, before we can do good works.
But this can not occur except through the faith that teaches us rightly to understand the Gospel and properly to lay hold of it. This is the only way in which Christ can be rightly known so that the conscience is satisfied and made to rejoice. Out of this grow love and praise to God who in Christ has bestowed upon us such unspeakable gifts. This gives courage to do or leave undone, and living or dying, to suffer every thing that is well pleasing to God. This is what is meant by Isaiah 9:6, “Unto us a child is born, unto us a son is given,” to us, to us, to us is born, and to us is given this child.
Therefore see to it that you do not find pleasure in the Gospel only as a history, for that is only transcient; neither regard it only as an example, for it is of no value without faith; but see to it that you make this birth your own and that Christ be born in you.
 Martin Luther, “Christmas Day (Luke 2:1–14),” in Luther’s Church Postil: Gospels: Advent, Christmas and Epiphany Sermons, ed. John Nicholas Lenker, trans. John Nicholas Lenker, vol. I, The Precious and Sacred Writings of Martin Luther (Minneapolis, MN: Lutherans in All Lands Co., 1905), 143–145.