Charles Ellicott Commentary Daniel 6:4

"Then the presidents and the satraps sought to find occasion against Daniel as touching the kingdom; but they could find no occasion nor fault, forasmuch as he was faithful, neither was there any error or fault found in him." — Daniel 6:4 (ASV)

Concerning the kingdom— that is, 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.