As Nebuchadnezzar watched what was happening inside the furnace, he marveled to see that the three Jews did not perish in an instant. Rising from his seat, he saw them loosed from their bonds and walking around inside the furnace. What startled him even more was the presence of a fourth person with them. The fourth person had an unusual appearance, like "a son of gods" (lit.). The king probably meant that this fourth person appeared to be super-human or divine from his viewpoint as a pagan polytheist. Evidently the fourth person was either an angel or the Angel of the Lord, the preincarnate Christ (cf. Genesis 16:13; et al.). He was with the three men in their affliction and protected them from harm in it (cf. Exodus 3:12; Psalm 23:4-5; Isaiah 7:14; Isaiah 43:1-3; Isaiah 63:9; Matthew 28:20). He did not deliver them from the fire but in it (cf. Romans 8:37). [source][source][source]