Malachi 4:4-6

Remember ye the law of Moses my servant, which I commanded unto him in Horeb for all Israel, even statutes and ordinances. Behold, I will send you Elijah the prophet before the great and terrible day of Jehovah come. And he shall turn the heart of the fathers to the children, and the heart of the children to their fathers; lest I come and smite the earth with a curse.