Albert Barnes Commentary Daniel 3:22

"Therefore because the king`s commandment was urgent, and the furnace exceeding hot, the flame of the fire slew those men that took up Shadrach, Meshach, and Abed-nego." — Daniel 3:22 (ASV)

Therefore, because the king’s commandment was urgent—Margin, as in Chaldee, “word.” The meaning is that the king would admit of no delay; he urged on the execution of his will, even at the imminent peril of those who were entrusted with the execution of his command.

And the furnace exceedingly hot—It was probably so hot as to send out flame far enough to make approaching it dangerous. The king's urgency would not admit of any arrangements, even if any could have been made, by which approaching it would be safe.

The flame of the fire slew those men—Margin, as in Chaldee, “spark.” The meaning is what the fire threw out—the blaze, the heat. Nothing can be more probable than this. It was necessary to approach the very mouth of the furnace to cast them in, and it is very conceivable that a heated furnace would belch forth such flames, or throw out such an amount of heat, that this could not be done except at the peril of life. The Chaldee word rendered “slew” here means “killed.” It does not mean merely that they were overcome with the heat, but that they actually died.

To expose these men to death in this way was an act of great cruelty, but we are to remember how absolute the character of an Eastern despot is, how much enraged this king was, and how regardless such a man would be of any effects on others in the execution of his own will.