"Behold, I will send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek, shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in: behold, he shall come, saith the LORD of hosts." — Malachi 3:1
"Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the LORD: 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."
"Jesus replied, "To be sure, Elijah comes and will restore all things. But I tell you, Elijah has already come, and they did not recognize him, but have done to him everything they wished. In the same way the Son of Man is going to suffer at their hands." Then the disciples understood that he was talking to them about John the Baptist". — Matthew 17:11-13
"Now this was John's testimony when the Jews of Jerusalem sent priests and Levites to ask him who he was. He did not fail to confess, but confessed freely, "I am not the Christ." They asked him, "Then who are you? Are you Elijah?" He said, "I am not." "Are you the Prophet?" He answered, "No." — John 1:19-21