Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword," Jesus told his disciples, twelve fresh recruits who on hearing that must have wondered what they were getting into. Jesus would later rebuke Peter for wielding a literal sword, and by that time, all twelve must have had at least a hint of the broader scope of Jesus' words.

Jesus' "sword"—the disruption his presence inevitably creates—has split families, neighborhoods, and nations. As the Misfit in one of Flannery O'Connor's stories puts it, "Jesus thrown everything off balance."

As I recently read the first two chapters of Luke, it struck me that the shadow of a sword hangs over Jesus' birth as well. We tend to recall the story in cheerful tones, but when Christ was born, menace filled the air.

"He will be a joy and delight to you," an angel prophesied to Zechariah about his son John. Yes, and a worry and a grief too, as reports filtered in of him eating bugs in the desert and incurring the wrath of Herod. As for John, he seemed to recognize his more famous cousin in utero: "The baby in my womb leaped for joy," Elizabeth told Mary when she learned of Mary's pregnancy. (Flash forward 30 years, though, when John would send a haunting question from prison: "Are you the one who was to come, or should we expect someone else?" John would feel the sword at its sharpest.)

I love the ironies embedded in Luke's Christmas story. While news of Elizabeth's pregnancy spread like gossip throughout the hill country of Judea, and her son John became a local hero for a time, poor Mary had to slip out of town to avoid the ugly accusations, and her son would be chased from the neighborhood by a murderous crowd. "A sword will pierce your own ...