Daniel 3:19 (BSB)

At this, Nebuchadnezzar was filled with rage, and the expression on his face changed toward Shadrach, Meshach, and Abednego. He gave orders to heat the furnace seven times hotter than usual,

From Daniel 3. Also in the ESV.

Commentary on Daniel 3:19

• John Calvin (Reformed), Calvin's Commentaries on Daniel 3:19: Here, at; first sight, God seems to desert his servants, since he does not openly succor them. The king orders them to be thrown into a furnace of fire: no help from heaven appears for them. This was a living and remarkably efficacious proof of their faithfulness. But they were prepared, as we have seen, to endure everything.
• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Daniel 3:19-27: In these verses we have, I. The casting of these three faithful servants of God into the fiery furnace. Nebuchadnezzar had himself known and owned so much of the true God that, one would have thought, though his pride and vanity induced him to make this golden image, and set it up to be worshipped, yet what these young men now said (whom he had...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Daniel 3:19: Then was Nebuchadnezzar full of fury,.... Nettled at the answer given him; perceiving his threats made no impression on these three men, and that they were resolutely determined at all events not to obey his will: and the form of his visage was changed against Shadrach, Meshach, and Abednego; not only to what it was in times past, when they were his favourites, and he...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Daniel 3:19: visage . . . changed--He had shown forbearance (Dan 3:14-15) as a favor to them, but now that they despise even his forbearance, anger "fills" him, and is betrayed in his whole countenance. seven times more than it was wont--literally, "than it was (ever) seen to be heated." Seven is the perfect number; that is, it was made as hot as possible.