The Messiah's coming would be announced by a man coming in the spirit of Elijah (John The Baptist).
OT Prophecy NT Fulfillment
Malachi 4:5
Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the LORD:
Matthew 3:1–2
[1] In those days came John the Baptist, preaching in the wilderness of Judaea,
[2] And saying, Repent ye: for the kingdom of heaven is at hand.

Matthew 11:13–14
[13] For all the prophets and the law prophesied until John.
[14] And if ye will receive it, this is Elias, which was for to come.
Tanakh – Neviim – Malachi 3:23
Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the Lord:
Hebrew OT – Malachi 3:23
[3:23] הִנֵּה אָנֹכִי שֹׁלֵחַ לָכֶם
אֵת אֵלִיָּה הַנָּבִיא
לִפְנֵי בּוֹא יוֹם יְהוָה
הַגָּדוֹל וְהַנּוֹרָא