Pastor Phillips Brooks' carol "O Little Town of Bethlehem" is one of my favorites. The fourth verse begins with this prayer:

O holy child of Bethlehem!
Descend to us, we pray;
Cast out our sin, and enter in,
Be born in us today!

"Be born—in us—today?" Billy E. Simmons asks, "In what way can the Christ of Christmas be born in us? How in heaven's name can such a thing as this take place?"

Simmons answers with these thoughts—most appropriate as we worship Jesus on Christmas day:

As we trust Christ for salvation, he comes to dwell in our hearts. By faith we open our hearts to him, and he is born in us anew. We speak of this event as a new birth or as salvation, and it is surely both of these. But in a very real sense the Christ of Christmas is born in us when we trust him as our Savior.

As we are born anew, and as we become extensions of the incarnation because the Christ of Christmas has been born in us, so we should share the joy of Christmas with others. There are so many around us who do not know the true joys of Christmas . . .. How sorely our world needs to hear the true message! They can hear it only as we will allow Christ to live out his ministry through us.

The rest of Brooks' carol completes the thought:

We hear the Christmas angels
The great glad tidings tell;
O come to us, abide with us,
Our Lord Immanuel!

The Lord Jesus concluded his commission to us to bear witness to him to the peoples of the earth with this promise: "As you go, I'll be with you, for as long as it takes" (Matthew 28:20, Carlisle translation). We'll realize his promise and recognize his presence as we go and as we tell.