Laws of the Medes and Persians
“Now, O king, ... sign the writing, that it be not changed, according
to the law of the Medes and Persians which altereth not.”- Daniel vi.
The Laws of Howel Dha,
who reigned in South Wales in the tenth century, printed with a
Latin translation by Wotton, in his Leges Wallicie
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894