The Aramaic verb azad (אֲזַד) means to be strong, firm, or firmly established. It appears in the Aramaic sections of Daniel and Ezra, used of decrees that are irrevocable — so firm that even the king cannot reverse them.
The irrevocable Medo-Persian decree serves as dramatic backdrop for Daniel's faithfulness — even an unalterable human law could not prevent God from delivering His servant. God's own decrees and promises are infinitely more firm: heaven and earth may pass away, but His Word stands forever (Matthew 24:35; Isaiah 46:10).