for as much as the king's word prevailed; and the furnace was made exceeding hot.
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Aquinas Study Bible
AD 2017
So that the king and the Babylonians would not think that they were seeing an illusion and the fire being harmless, God caused many of those who had gathered around the furnace to be consumed.
Slew. They were working still at the furnace, when it burst out and destroyed them, (Calmet) while the three Jews were praising God below. (Haydock) (ver. 46, 48.)
Of course this meant the same men of whom it was said above, "And he commanded the strongest men in his army to bind the legs of Shadrach, Meshach and Abednego and cast them into the burning furnace of fire (another reading: into the furnace of flaming fire)." And so they were not any chance servants of his whom Nebuchadnezzar destroyed, but men who of all his army were strong and most ready for war. Not only was it intended that the miracle should strike terror but also that his own army might experience injury.