Today we have a momentous gathering of thousands of Jews . Mordechai Hatzadik also arranged a large gathering when facing our enemies.
The verse states וַיֵּצֵא֙ בְּת֣וֹךְ הָעִ֔יר וַיִּזְעַ֛ק זְעָקָ֥ה גְדֹלָ֖ה וּמָר׃, He went through the city, crying out loudly and bitterly (Esther, 4:1)
Rav Shlomo Halevi in his sefer Manos Halevi on the Megillah offers a beautiful explanation as to what he was doing. He says the definition of ויזעק זעקה גדולה refers to the large gathering of the nation according to. He used his voice to gather the nation.
He used the specific type of tefillah called זְעָקָ֥ה.
Mordechai said, We don’t have any king, or (president so to speak) to rely on. We don’t have a Navi who can daven for us. We have no place to run or escape. No country to go to that will provide us safety. We are like sheep that have no shephard; or like a ship in the ocean with no captain to navigate it. We are like orphans with no father.
He then brought out a sefer Torah accompanied with words of tefillah. What type of words did he use? Words of fire, words that would break the hearts of the people to return them to Hashem.
His armor and weapons were tefillah and entreaties to Hashem. Tefillah is what protects the person as a protective armor protects a person in a physical war. His davening was a great tefillah, with a bitter heart.
He said to Hashem, Yitzchak, my father heard the one sound (tzaaka gedolah) of Eisav and, what did you do? You blessed him. Behold, we, (our entire nation) are being threatened with death by the sword, and Mordechai therefore davened a זעקה גדולה.
Mordechai was not a crying out to the king nor was it to the nation, instead it was a pure tefillah to Hashem. The large gathering was used in his Tefillah for Hashem.
Mordechai said to Hashem, that for only one cry, of one person Eisav, he was blessed. Why did he cry? Because of him not receiving a certain good that he actually relinquished. And, nevertheless his father Yitzchak blessed him.
How much more so it is befitting that our tefillos should be heard, when Hashem hears and sees this large gathering of the nation in prayer and outcry, facing annihilation, and death at the sword.
(The above is based on my understanding of the Manos Halevi on this pasuk)
May this large gathering of our nation of Yisrael today carry with it the zechus of Mordechai Hatzadik’s great tefillah to Hashem; as our armor and weapons to protect Klal Yisrael when facing our enemies. May all our hearts be pierced, to continue to unite and draw close to Hashem, and humbly see the revelation of His Unity.