Following Esther's urgent directive to gather the Jewish people and declare a fast, Mordecai sprang into immediate action. Leveraging his high standing among the people, he successfully assembled them, and they readily accepted his authority [ביאור שטיינזלץ]. He departed from Esther's presence to act without a moment of delay [אור חדש]. Rather than sending a messenger, he gave up his personal honor and walked through the streets of Shushan himself to gather the people and deliver Esther's message [מלבי״ם, רלב״ג, עמנואל הרומי, יוסף אבן יחיא, אלשיך]. Some suggest he crossed a river that separated the capital from the main city [אבן עזרא]. Others note that he might have simply stepped over a small puddle to reach the people, demonstrating that even the smallest physical effort made for the sake of a commandment is noted and recorded [תורה תמימה, מנות הלוי]. On a deeper spiritual level, crossing water symbolizes moving past the accusers and hostile nations. These opposing forces are compared to rushing waters that attempt to block the prayers of Israel from ascending to heaven [אור חדש].
Mordecai's actions also involved a bold breaking of standard norms. The primary approach among commentators is that he violated Jewish law by declaring a fast on the first day of the Passover holiday. He did this with the clear understanding that if there is no Israel, there can be no Torah and no Passover. Another perspective suggests he actually altered Esther's specific command. While she requested the fast to begin instantly, he delayed it slightly so the people could properly prepare themselves in holiness and purity [אלשיך]. Furthermore, his actions were fueled by intense sorrow and anger over the harsh decree, leading him to cancel the traditional joy of the holiday [מנות הלוי].
Internally, Mordecai experienced a profound mental shift, completely removing any previous suspicions he might have held regarding Esther. This moment also marked a significant role reversal between them. While Esther had previously followed Mordecai's instructions, he now obeyed her, treating her words with the weight of a royal command [שלום אסתר, יוסף אבן יחיא].
Mordecai did not settle for making a basic public announcement but personally ensured that every detail was carried out [אלשיך]. The response he orchestrated went far beyond simply avoiding food and drink. It was a comprehensive process of repentance designed to atone for the Jewish people participating in King Ahasuerus's feast. This massive effort included wearing sackcloth, throwing ashes, weeping aloud, blowing shofars, and holding Torah scrolls. They even went so far as to separate nursing infants from their mothers to awaken God's mercy [מנות הלוי, אור חדש, יוסף אבן יחיא].
Regarding the specific duration of the three-day fast, God does not leave righteous people in distress for more than three days. The number three represents a measure of honesty and justice. Through the merit of their deep devotion to the Torah, or perhaps the historical merit of the self-sacrifice shown during the Binding of Isaac, the people earned the right for their fast to be accepted, ensuring their salvation on that crucial third day [אור חדש].