Daniel 6:12-15

12Then they approached and spoke before the king regarding his injunction, “Have you not signed an injunction that anyone who petitions (prays to) any god or man except you, O king, within the designated thirty days, is to be thrown into the den of lions?” The king answered, “The statement is true, in accordance with the law of the Medes and Persians, which may not be altered or revoked.”

13Then they answered and said before the king, “Daniel, who is one of the exiles from Judah, does not pay any attention to you, O king, or to the injunction which you have signed, but keeps praying [to his God] three times a day.”

14Then, as soon as the king heard these words, he was deeply distressed [over what he had done] and set his mind on rescuing Daniel; and he struggled until the sun went down [trying to work out a way] to save him.

15Then, by agreement, these same men came to the king and said, “Know, O king, that it is a law of the Medes and Persians that no injunction or statute which the king establishes may be altered or revoked.”