John Calvin Reformed @genevareformer

Here Daniel answers the king moderately and softly, although he had been cast into the cave by his command. He might have deservedly been angry and expostulated with him, because he had been so impiously deserted by him, for King Darius had found him a faithful servant, and had used his services for his own advantage.

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. The melancholy night which the king had, upon Daniel's account, Dan 6:18. He had said, indeed, that God would deliver him out of the danger, but at the same time he could not forgive himself for throwing him into the danger; and justly might God deprive him of a friend whom he had himself used so barbarously.

Commenting on Daniel 6:18-24

John Gill Reformed Baptist @doctorgill

My God hath sent his angel,.... Daniel takes up the king's expression, and confirms it; he asserts God to be his God, of which he had given him a proof in sending his angel to him that night; either one of the ministering spirits about him, or the Angel of the covenant, the same with him, said to be like the Son of God, that...