Luke 1:41
And it came to pass, that, when Elisabeth heard the salutation of Mary, the babe leaped in her womb; and Elisabeth was filled with the Holy Ghost: And it came to pass, that, when Elisabeth heard the salutation of Mary, the babe leaped in her womb; and Elisabeth was filled with the Holy Ghost:
Mary's visit to Elizabeth was the setting for a manifest working of the Holy Spirit's power. In that meeting the leaping in the womb was the unborn John responding to the presence of Jesus. At that same moment Elizabeth herself was filled with the Holy Ghost. The whole event thus bears witness that Jesus is the Promised One.