What does the Bible say about the ministry of Elijah?

In Malachi 4:5-6, God promises to send Elijah the prophet before the great and dreadful day of the Lord. This prophecy is understood to be fulfilled in the ministry of John the Baptist, who prepared the way for Christ. Jesus Himself affirms this in Matthew 11:11, recognizing John as the greatest of the Old Testament prophets. John's ministry was not only historical but also spiritual, serving to turn the hearts of the disobedient and to bring people to repentance, thus preparing them for the arrival of the Messiah.