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It is exactly like the question: “what IS the title of the book, which has not been placed unto my desk YET, but might be placed upon that desk sometime in the future”. There is no “correct” answer to this question, because it refers to an event which has not happened YET, and might not even happen in the future.
but there is a correct answer, don’t assume that because you are limited that then an infinite God must be limited.
the book which is not on your desk yet is ‘the messenger who shall prepare the way for the Lord’. and this books title is Elijah.
…in the Book of Malachi 3:1 that refers to a prophet who would prepare the way of the Lord:
“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[29]
and also at the end of the next chapter in Malachi 4:5-6 where it says,
“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.”
The Jews of Jesus’ day expected Elijah to come before the Messiah; indeed, some modern Jews continue to await Elijah’s coming as well, as in the Cup of Elijah the Prophet in the Passover Seder. This is why the disciples ask Jesus in Matthew 17:10, ‘Why then say the scribes that Elias must first come?.’ The disciples are then told by Jesus that Elijah came in the person of John the Baptist,
“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