Daniel 6:8-10 (King James Version)
8 Now, O king, establish the decree, and sign the writing, that it be not changed, according to the law of the Medes and Persians, which altereth not.  9 Wherefore king Darius signed the writing and the decree. 10 Now when Daniel knew that the writing was signed, he went into his house; and his windows being open in his chamber toward Jerusalem, he kneeled upon his knees three times a day, and prayed, and gave thanks before his God, as he did aforetime.
Daniel 6:12 (King James Version)
12 Then they came near, and spake before the king concerning the king's decree; Hast thou not signed a decree, that every man that shall ask a petition of any God or man within thirty days, save of thee, O king, shall be cast into the den of lions? The king answered and said, The thing is true, according to the law of the Medes and Persians, which altereth not.
6:8 altereth not: Chaldee passeth not