Ezra 4:6 Commentary - English Annotations on the Holy Bible by Matthew Poole

In the reign of Ahasuerus; which is supposed by divers learned men to be from this time a common name to divers succeeding kings of Persia. And this makes it seem doubtful who this was. This was either,

1. Xerxes the fourth and rich king of Persia, as he is called, Dan 11:2. Or rather,

2. Cambyses the son and successor of Cyrus, as may appear,

1. Because none but he and Smerdis were between Cyrus and this Darius.

2. Because Cambyses was known to be no friend to the Jewish nation nor religion; and therefore it is very improbable that these crafty, and malicious, and industrious enemies of the Jews would omit so great an opportunity when it was put into their hands.