Who Is The Elijah That Would d Come Before The Great Day of the Lord?

Why does the Bible teach that Elijah must first come before the great and awesome day of the Lord? Who is Elijah? Some have claimed it was Elijah Muhammad of the Muslims. Does this fit the text or is it for a time far removed from the text. Elijah was essential to the end time to occur. But mystery surrounds him. Some believe his apearance will be reincarnation. Today's lesson will cover some of the details of Elijah's return.