Reference

Luke 1:39-56
  "Bursting with Joy"

In this passage we are confronted with outbursts of joy, all the result of what God is doing.  Mary, pregnant with the promised messiah, Elizabeth, pregnant with John the forerunner of Jesus, and even John, still in the womb, burst with joy!  God is fulfilling his promises!  God is acting to redeem his people!  This gospel truth is the source of ultimate joy that lasts, even when lesser joys of this world fade away.