Why does Jesus say that John the Baptist is the “Elijah who was to come” in Mat 11:13, but then John the Baptist denies that he is Elijah in John 1:21?
These passages address or allude to the prophesied necessity of a forerunner coming prior to the coming of Christ. The confusion exists, as it does with many other places in prophecy, over the nature of the coming of Christ. That coming is in two parts – we had the first coming whereby Christ goal was to pay the penalty for sin, and the second coming in which He will establish His kingdom. These two comings are often confused and that is because they are often in the same context. In Malachi 3:1 we have the obvious reference to the forerunner at the first coming of our Lord (John the Baptist), but in Malachi 4:5 (the same general context) we have the prophecy that Elijah will come before the “day of the Lord” (we now know “the day of the Lord” is a reference in Scripture to Christ second coming). This same prophecy is likely why John was asked the question in John 1:21, if he was Elijah, which John denied.
Both John the Baptist and Elijah had similar ministries – he dressed like Elijah, ministered like Elijah, had a message of judgment like Elijah (2 Kings 1:7-8 & Matt 3:4). In Luke 1:17 John the Baptist is stated by the prophesying angel as “a forerunner in the spirit and power of Elijah” and then quotes the same context as Malachi 4:5 regarding Elijah’s stated role “to turn the hearts of the fathers back to the children, and the disobedient to the attitude of the righteous so to make ready a people prepared for the Lord.” This then is the key to understanding what Christ meant when He stated in Matt 11:13-14 “And if you are willing to accept it, John himself is Elijah who was to come.” This is further clarified in Matt 17:10-13. Here when Christ is asked the question about Elijah as the forerunner, He both states that Elijah will come (Matt 17:11), and has already come (Matt 17:12-13) in the form of John the Baptist (who came in the spirit and power of Elijah). John the Baptist was the forerunner of Christ’s first coming (in the spirit and power of Elijah), and Elijah will yet come as a forerunner to Christ’s second coming.
Now, let’s put the puzzle together to understand what Christ was saying about John the Baptist as Elijah. First, we see that John the Baptist denies that he is Elijah (John 1:21). He was not physically Elijah. John was born to Zacharias and Elizabeth (Luke 1). However, he did come in the spirit and power of Elijah, and his purpose was the same as Elijah’s in that he was to prepare the people to receive the Lord Jesus (Mal 4:5 & Luke 1:17). So on the one hand he was not physically Elijah, but on the other hand he had the exact role as Elijah “to prepare the hearts to receive Christ when He comes.” This second aspect is clearly what Christ is referring when in Matt 11:1-15 He is answering first John the Baptist’s question, and then speaking to His disciples about the role of John the Baptist. The phrase “if you are willing to accept, John himself is Elijah who was to come” has referral in the context to his role has the forerunner (Matt 11:10). In other words, for those that do accept Christ as the Messiah in His first coming, John fulfills the role of Elijah “to restore the hearts of the people…etc”. This is the “if you are willing to accept” person. This is also the logical explanation of the “has come” and “will come” role that is seen in Matt 17:10 -13. For the nation as a majority that did not accept Christ as their Messiah at His first coming, John the Baptist was not their Elijah (as the forerunner), and there is yet the forerunner to come before Christ’s second coming who will fulfill that role. There are many references in Scripture to the yet coming awakening of Israel to their Messiah (Zech 12:10; Rom 11:25-27) under the new covenant. Many scholars believe that of the two witnesses prophesied in Revelation 11, one of those witnesses matches the description of Elijah - his appearance being during the tribulation. Of this we cannot be dogmatic, but do believe from what Christ has stated, there will yet be the appearance of Elijah prior to the second coming of Christ to have the role to prepare the hearts of the people to receive Him.