Daniel 6:8

It be not changed. On the irrevocability of the law of “the Medes and Persians” compare Esther 1:19; 8:8. This characteristic is also attested by Greek writers. For example, Diodorus Siculus (xvii. 30) describes the attitude of Darius II toward the sentence of death upon Charidemos. He claims that the king, after pronouncing the death sentence, repented and blamed himself for having greatly erred in judgment; yet it was impossible to undo what had been done by royal authority.

Medes and Persians. Higher critics frequently pointed to the presence of this expression in the book of Daniel, used at a time when the Persians were actually more in control of the former empire than the Medes, as proof of the supposed late authorship of the book. They claimed that such a term would be used only at a time when the real political situation had become hazy in the memory of the people. Contemporary documents, since discovered, have proved this higher critical view incorrect. These documents refer to the Persians as “Medes,” and to “Medes and Persians,” as does the Bible. The cuneiform documents also mention various Persian kings by the title “king of the Medes,” as well as by the customary title “king of Persia”. Since Darius was a “Mede,” it is only natural that any courtier referring in his presence to the law of the land would speak of “the law of the Medes and Persians”.