He will go before him in the spirit and power of Elijah, 'to turn the hearts of the fathers to the children,' and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord."
Turn the hearts of the fathers to the children ... etc.  These are plainly the words of  Malachi 4:5,6; but what do they mean?  There seems to be a metaphor here in which the fathers, Abraham, Isaac, Jacob, etc. have turned away their hearts from the rebellious Israelites.  Therefore, the preaching of the great herald will cause many to repent, leading to turning the fathers' hearts to the children.