Then the king went to his palace, and passed the night fasting: neither were instruments of music brought before him: and his sleep went from him.
All Commentaries on Daniel 6:18 Go To Daniel 6
Jerome
AD 420
How sincere was the king's good will, when he would not touch food night or day or grant his eyelids sleep, but as long as the prophet was in danger he himself remained in a state of sympathetic suspense. But if a king who knew not God did such a thing for another man whose deliverance he desired, how much more ought we to implore God's mercy for our own sins with fastings and watchings.