The Prophet Elijah was to plant in the hearts of the children the promises made to their fathers,
Foreshadowing the great work to be done in the temples of the Lord in the dispensation of the fulness of times, for the redemption of the dead, and the sealing of the children to their parents, lest the whole earth be smitten with a curse and utterly wasted at his coming.
Doctrine & Covenants 138:47-48
Read in scriptures: http://bit.ly/1UDmN1j