כשבת המלך אחשורוש על כסא מלכותו אשר בשושן הבירה
“When King Achashveirosh sat on his throne, which was in the capital city Shushan." (Esther 1:2)
The Shulchan Aruch (690:3) rules: צריך לקרותה כולה – “One must read the entire Megillah." The Mishnah Berurah adds: “According to most poskim, if you didn’t hear just one word of the Megillah you aren't yoitza [haven’t fulfilled your duty].”
The meforshim explain that this is because every pasuk and every word of the Megillah expresses another part of the miracle. So, if you missed a word, you missed a brick in the miracle.
The Megillah begins (1:2): כשבת המלך אחשורוש על כסא מלכותו אשר בשושן הבירה – “When King Achashveirosh sat on his throne, which was in the capital city of Shushan." The Vilna Gaon explains that Shlomah HaMelech had a magnificent throne. Many kings wanted to sit on it but failed. Pharaoh Nakeh (Pharaoh the Lame) sat on Shlomah HaMelech’s throne, and one of the decorative lions bit him, and that's how he became lame. Nevuchadnetzar also wanted to sit on Shlomah’s throne and failed.
Achashveirosh also wanted to sit on a magnificent throne similar to Shlomah's, so he sought craftsmen to fashion a replica of this unique throne. The craftsmen who knew how to build such a majestic chair lived in Shushan. When it was completed, it was too heavy to transfer to Bavel, so Achashveirosh moved the capital city to Shushan. Shushan became the new capital city of the Persian Empire.
The Vilna Gaon writes: “This is the meaning of: כשבת המלך אחשורש ... בשושן, Achashveirosh was the first king to live in Shushan. All the kings before him didn’t live there. This is recorded in the Megillah so we will recognize Hashem's wonders and understand that Hashem prepared every step that led up to the miracle for Bnei Yisroel. Mordechai and Esther lived in Shushan, so Hakodosh Boruch arranged that Achashveirosh should move his capital there."
This is the astounding miracle implied in this pasuk. The two gedolim of Bnei Yisroel, Mordechai and Esther, from whom will come the salvation for Bnei Yisroel, lived in Shushan, so Hashem arranged that Achashveirosh should move his capital city to Shushan, right near where they lived! When Haman passed his evil decrees, Mordechai and Esther were on the scene and were able to thwart Haman's evil plans.
The Vilna Gaon adds: “Chazal tell us that one must read the entire Megillah, even the parts that are seemingly superfluous. For example, why is knowing about Achashveirosh’s wealth and power important? However, every pasuk of the Megillah tells us another facet of this great miracle.”
This also reveals Hashem’s love for His tzaddikim and the Jewish nation. Hashem could have had Mordechai and Esther move to the capital city in Bavel, where all Persian kings lived. But Hashem had Achashveirosh and his entire cabinet move to Persia rather than have Mordechai and Esther come to Bavel.
The Rambam (introduction to Pirush HaMishnayos) discusses that Hashem takes exceptional care of his tzaddikim. He writes that Hakodosh Boruch Hu can give a king a desire to build a beautiful palace, and “perhaps the palace was built for a chossid who will stay there one night many years later, and his life will be saved when he stays there.” Similarly, in our story, Achashveirosh moves to Shushan, but it is all for Mordechai, Esther, and the Jewish nation.
