John the Baptist Denies Being the Messiah
19 Now this was John’s testimony when the Jewish leaders in Jerusalem sent priests and Levites to ask him who he was. 20 He did not fail to confess, but confessed freely, “I am not the Messiah.”
21 They asked him, “Then who are you? Are you Elijah?”
He said, “I am not.”
“Are you the Prophet?”
He answered, “No.”
22 Finally they said, “Who are you? Give us an answer to take back to those who sent us. What do you say about yourself?”
23 John replied in the words of Isaiah the prophet, “I am the voice of one calling in the wilderness, ‘Make straight the way for the Lord.’”
24 Now the Pharisees who had been sent 25 questioned him, “Why then do you baptize if you are not the Messiah, nor Elijah, nor the Prophet?”
26 “I baptize with water,” John replied, “but among you stands one you do not know. 27 He is the one who comes after me, the straps of whose sandals I am not worthy to untie.”
Do you know why he denied that he was Elijah?
His answer in the last line tells us why. His only calling and ministry was to prepare the way of the one who would come after him. This imagery is absolutely clear to the Jews who were questioning him, he is taking on the mantle of Elijah without calling himself Elijah. They understood this because that was indeed their expectation. They expected Elijah to announce the coming of the Messiah.
As I said earlier, he worked on their expectations but not once is Elijah supposed to announce the coming of the Messiah. There is not a single verse in the bible that defends this idea. So where did the Jews get the idea from?
They got it from a verse I quoted earlier but will copy paste here so that you can see it again and realize its importance and that John the Baptist did nothing in denying that he was Elijah. It would have been a falsehood and God does not do falsehood.
5 “See, I will send the prophet Elijah to you before that great and dreadful day of the Lord comes.
So will Elijah come, to announce the coming of the Messiah or is it rather as the verse states, that he will come before that great and dreadful day, the Lord comes?
Some people thought that this verse meant the Messiah, but it doesn't mean that at all. It is a reference to something known throughout the bible as "The Day of Wrath", mentioned by prophets throughout the entire Bible. We are better acquainted with the idea under another term... the Great Tribulation.
Your Idea that Malachi's Prophecy of the return of Elijah was not denied by John The Baptist does not ring true with the Bible , because John denied that he was Elijah the Jews could not accept Jesus as the Messiah.
Jesus disciples were confronted by the fact that the Jewish leaders denied Jesus as the messiah, because if it were so where was Elijah who was to preceded him?
When the disciples returned to Jesus he told them that if they could accept it, John the Baptist was indeed Elijah who is to come.
Jesus was trying to teach them that Elijah is a mission not just a man and his mission was to draw the people of Israel or convince them that Jesus was the Messiah.
The Fact that John the Baptist said "I'm not worthy to tie his saddles " was NOT a clear indication or Identification that Jesus was the Messiah to the this question. It was a total denial that he was Elijah or even a prophet. And the very reason they ask this is because they were told to expect the prophet Elijah before the Coming of The Lord, and this is why Jesus had to testify John was this man.
Malachi is the last book of Prophesy in the OT, the scripture is
Malachi 4 :5,6
"But before the great and terrible day of The Lord comes, I will send you the Prophet Elijah. 6.He will bring fathers and children together again;otherwise I would have to come destroy your country"
This is a quote of the full verse., the tail end of which you chose to not include.