The Arrival of Mashiach
Question
How will the Jewish people know when the Mashiach is here?
Answer
Shalom!
Thank you for your question.
There are several sources that address your question.
Let’s us begin with a look at the Rambam’s “Iggeret Teiman” in chapter 4.
“With respect to Mashiach’s arrival, he will not be known beforehand until it is declared to him… a man, unknown prior to his manifestation, will rise, and the signs and wonders that will come about through him will be the proof for the authenticity of his claim and pedigree…”
Mashiach can come at any time. He is already on earth. There is a righteous person who is qualified to be the Mashiach in every generation. On the day that G-d will decide to redeem us reveal the Mashiach, who will be the leader of the Jewish people, a unique pre-existing soul, known as the soul of Mashiach will descend upon him. (somewhat similar to the idea that every Jew receives an additional soul on Shabbat).
As the Chatam Sofer 6:98 writes, “As for the coming of the scion of David, I suggest the following: Moses the first redeemer of Israel, reached the age of eighty years and did not know or sense that he would redeem Israel. Even when the Holy One, blessed be He, said to him, ‘Come and I will send you to Pharaoh…’ (Ex. 3:10), he declined and did not want to accept that mission. So, it will be with the final redeemer.”
“The very day that the Bet Hamikdash was destroyed, was born one who, by virtue of his righteousness, is fit to be the redeemer. At the proper time G‑d will reveal Himself to him and send him, and then will dwell upon him the spirit of Mashiach which is hidden and concealed above until his coming."
So too, it says: “The righteous man [potential Mashiach] himself does not realize this potential. Because of our sins many such people passed away already. We did not merit that the Messianic soul be conferred upon them. They were fit and worthy, but the generations were not fit…” (Based on Yerushalmi, Berachot 2:4, and Eichah Rabba 1:5)
In summary: The Mashiach will know that he has been appointed Mashiach and he will prove to us that he is the chosen redeemer.