Daniel 6:14-15

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.”