Cyrus, king of Persia, began with one of the most generous decrees in biblical history. He ended with one of the most foolish. SAFE0 Rabbah traces exactly where his words went wrong.
Rabbi Hanina bar Ada opened with Ecclesiastes: "The words of the mouth of a wise man are grace, and the lips of a fool will swallow him" (Ecclesiastes 10:12). The wise beginning was Cyrus's famous proclamation: "So said Cyrus king of Persia: The Lord, God of the heavens, has given me all the kingdoms of the earth and He has commanded me to build Him a house in Jerusalem, which is in Judah" (Ezra 1:2). So far, so good. Cyrus acknowledged God as the God of the heavens and accepted a divine mission to rebuild the Temple.
But then he kept talking. "He is the God who is in Jerusalem" (Ezra 1:3). With that single phrase, Cyrus reduced the God of the heavens to a local deity, the God of one city. The lips of a fool had swallowed him.
It got worse. Ecclesiastes continues: "The beginning of the words from his mouth is foolishness and the result from his mouth is evil debauchery" (Ecclesiastes 10:13). What was the foolishness? Cyrus said, "Any of you from all His people, may his God be with him" (Ezra 1:3), implying that other nations have their own gods. And then the real damage: he decreed that whoever had already crossed the Euphrates could stay, but whoever had not crossed could not go. He cut off the migration at an arbitrary point.
The midrash (rabbinic interpretive commentary) then applies the same Ecclesiastes verse to Ahasuerus. "At the beginning of his reign, they wrote a libel against the residents of Judah and Jerusalem" (Ezra 4:6). The result of his mouth was evil indeed: he canceled the work on the Temple entirely. When everyone saw this, they screamed: "Woe!" And so the Book of Esther begins: "It was during the days of Ahasuerus" (Esther 1:1).