What does Daniel 3:21 mean?

But if not, let it be known to you, O king, that we will not serve your gods or worship the golden image which you have set up.”

Then Nebuchadnezzar was full of fury, and the form of his appearance was changed against Shadrach, Meshach, and Abednego. He spoke, and commanded that they should heat the furnace seven times more than it was usually heated.

He commanded certain mighty men who were in his army to bind Shadrach, Meshach, and Abednego, and to cast them into the burning fiery furnace.

Therefore because the king’s commandment was urgent, and the furnace exceeding hot, the flame of the fire killed those men who took up Shadrach, Meshach, and Abednego.

These three men, Shadrach, Meshach, and Abednego, fell down bound into the middle of the burning fiery furnace.

Then Nebuchadnezzar the king was astonished, and rose up in haste. He spoke and said to his counselors, “Didn’t we cast three men bound into the middle of the fire?” They answered the king, “True, O king.”