Your wife Elizabeth will bear you a son, and you are to give him the name John. He will be a joy and delight to you, and many will rejoice because of his birth, for he will be great in the sight of the Lord ... Many of the people of Israel will he bring back to the Lord their God. And he will go on before the Lord, in the spirit and power of Elijah, to turn the hearts of the fathers to their children and the disobedient to the wisdom of the righteous—to make ready a people prepared for the Lord.
Source: Bible - Luke 1:13-17