Concerning the kingdom — i.e., in his official capacity. The plan of the conspirators was to place Daniel in such a situation that his civil and religious duties might be forced to clash with each other.
Related Commentaries of Daniel 6:4
Daniel 6:4
4 Then the presidents and princes sought to find occasion against Daniel concerning the kingdom; but they could find none occasion nor fault; forasmuch as he was faithful, neither was there any error or fault found in him.