The Gemara states: The Roman Empire leaves and the Persian Empire enters after her. Why does the Persian Empire follow the Roman Empire? The reason is because they are the most distinguished following the Romans. How do we know that the Persians are the most distinguished after the Romans? It is said (Daniel 7:5) and behold! Another beast, a second one, similar to a bear. And Rav Yosef taught in a Baraisa: this refers to the Persians who eat and drink like a bear, they are thickly coated with flesh like a bear, they grow hair like a bear, and they also do not rest like a bear.
It is said (Esther 1:2) בַּיָּמִים הָהֵם כְּשֶׁבֶת הַמֶּלֶךְ אֲחַשְׁוֵרוֹשׁ עַל כִּסֵּא מַלְכוּתוֹ אֲשֶׁר בְּשׁוּשַׁן הַבִּירָה, in those days, when King Achashverosh sat on his royal throne which was in Shushan the capital. The Medrash (Esther Rabbah 1:10-11) states: this is one of those times when the angels were casting notes in protest before HaShem. They said, “Master of the Universe! The Bais HaMikdash lies in ruins and this wicked one, Achashveirosh, sits and makes parties.” HaShem responded, “place days opposite days,” as it is said (Nechemia 13:15) בַּיָּמִים הָהֵמָּה רָאִיתִי בִיהוּדָה דֹּרְכִים גִּתּוֹת בַּשַּׁבָּת, in those days I observed in Yehudah people treading on winepresses on Shabbos.
The Medrash (Ibid) continues expounding the words בַּיָּמִים הָהֵם כְּשֶׁבֶת הַמֶּלֶךְ אֲחַשְׁוֵרוֹשׁ, when King Achashveirosh sat on his royal throne. Rabbi Yitzchak said: the nations of the world do not have any permanent residence in this world. They asked Rabbi Yitzchak from this verse, which states that King Achashveirosh sat on his royal throne, which indicates that the nations of do have a permanent residence. Rabbi Yitzchak responded, it does not say בשבת המלך, “when” the king was sitting on his royal throne. Rather, it is said כשבת המלך, “like” the king was sitting, implying a siting that was not a real sitting, whereas the sitting of the Jewish People is a permanent sitting, as it is said (Shoftim 11:26) בְּשֶׁבֶת יִשְׂרָאֵל בְּחֶשְׁבּוֹן וּבִבְנוֹתֶיהָ, while Israel dwelt in Cheshbon and its suburbs.
We can suggest that this Medrash is proof to the Gemara’s statement that the Persian Empire does not rest akin to a bear. Achashveirosh was from the Persian dynasty, and his “sitting” on the throne was not an actual sitting. Furthermore, the Jewish People are required to rest on Shabbos, and the nations of the world are prohibited from resting on Shabbos (Sanhedrin 58b). Yet, when the Jewish People violate the Shabbos, as occurred in the days of Nechemia, only then do the nations of the world attain a perceived rest.