John Calvin Reformed @genevareformer

Here the king begins to act with a little more consistency, when he approaches the pit. He was formerly struck down by fear as to yield to his nobles, and to forget his royal dignity by delivering himself up to them as a captive. But now he neither dreads their envy nor the perverseness of their discourse.

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

And when he came to the den, he cried with a lamentable voice unto Daniel,.... Expressing grief and sorrow his heart was full of; it was rather like howling than speaking; thus he cried before he saw Daniel, or heard him speak: when he was near to the den (k), as it may be rendered; and he was between hope and fear about Daniel's safety...